Here's a basic rundown of the forms.
"The Seven Forms Of Lightsaber Combat
Form I: Shi-Cho or the Determination Form was the first of the seven forms of lightsaber combat
"It is simple, and its simplicity is its strength."
—Kreia
As the weapons technology of the lightsaber was developed, the need for a form of combat arose. Thus Form I, also called Way of the Sarlacc, was born. Shii-Cho was the most ancient style of lightsaber combat, developed by early Jedi Masters to incorporate key principles of ancient sword-fighting traditions.
One of the marks of contact, sun djem, was a goal of early Form I duelists, as disarming or destroying the opponents' weapons could ensure victory without causing injury, which was always a Jedi objective. However, with the rise of Form II, sun djem became nearly impossible as Makashi duelists were well trained to prevent their own weapons being taken or destroyed.
During the Old Jedi Order, Younglings started out by learning Form I before beginning a Padawan apprenticeship with a Jedi Master. Their training included learning to deflect plasma bolts from training remotes while being blindfolded or covered up by a practice helmet. Lightsaber instructors such as Yoda and Cin Drallig taught Form I to thousands of students during their Jedi careers.
Form II: Makashi or The Contention Form was the second form of the seven forms of lightsaber combat.
"He is a fencer. Leverage, position, advantage—they are as natural to him as breathing."
—Qui-Gon Jinn's spirit to Yoda on Count Dooku
After Form I's proliferation as a lightsaber combat technique, Form II, or Way of the Ysalamiri, came about as a means of lightsaber-to-lightsaber combat. It was described as being very elegant, powerful, and requiring extreme precision, allowing the user to attack and defend with minimal effort, often wielding the blade one-handed for greater range of movement and fluidity. The form relied on parries, thrusts, and small, precise cuts—as opposed to the blocking and slashing of the other forms. It required very fluid movements of both the blade and the body. Form II countered sun djem, the goal of early Form I masters, by being well trained in prevention of disarming and weapon destruction.
The opening stance for Makashi is a single-handed low guard, with the blade angled downward at the practitioner's side. The formal salute that Dooku offered Yoda on Geonosis was a "Makashi salute," while a Makashi flourish consisted of drawing a rapid X in the air with the blade.
Feints would also be commonly used to confuse or set-up their opponents for a trap, a tactic that Count Dooku commonly used in his duels during the Clone Wars. Precise footwork and movements were required for maintaining proper distance from the opponent during defense and/or when moving in for an attack. The blade manipulation required for this form was very refined and required intense focus. Timing, accuracy, and skill, rather than strength, were relied on to defeat one's opponent, and with a skilled practitioner, the results were extremely potent.
Form III: The Resilience Form was the third form of the seven forms of lightsaber combat
"That is so like you, Master Kenobi. I am called a great swordsman because I invented a lethal style; but who is greater, the creator of a killing form—or the master of the classic form?"
—Mace Windu to Obi-Wan Kenobi
Form III was originally developed to counteract the advancing blaster technology throughout the Galaxy. Those to whom the Jedi were mainly opposed usually wielded blasters, and the Jedi needed to find a method of defense that could repel normally overwhelming volleys of blaster fire. Soresu was then founded upon the basic deflection principles all Padawans were taught, the skill that enable them to protect themselves from blaster bolts.
The third form of lightsaber combat utilized motions that occurred very close to the body, in an attempt to achieve near-total protection and expend as little energy as possible while executing moves. This technique minimized the body's exposure, making a well-trained practitioner nearly invincible. Followers of Soresu comfortably remained on the defensive until their opponent left an opening that a Soresu practitioner usually could exploit in multiple ways. Soresu was best described as a passive form of combat, and one that was used by those who were extremely patient and reserved.
Due to the emphasis on defense training, Form III involved preparation for prolonged battles so that the user would be able to learn as much as possible about their opponent or opponents while engaged in possibly deadly combat. Also, by being more capable in lengthy battles, a Soresu user was in a position to gain control of the situation and provide multiple options for the duelist; such as the choice to either kill, disarm, or even reason with their opponent. Many Soresu practitioners survived the Battle of Geonosis, thanks in part to its specialization in fending off blaster fire. Soresu's greatest power lay in the endurance and control a practitioner eventually developed. Masters of the form left no opening for their opponents to take advantage of, while waiting for the eventual lapses in their opponent's own defense.
Form IV: Ataru, the Agression Form, was the fourth form of the seven forms of lightsaber combat
Ataru was an aggressive combat form relying on a combination of power, speed, and grace. Practitioners of Ataru were always on the offensive, attacking with wide, fast, and powerful swings. Form IV practitoners constantly called upon the Force to aid in their movements and attacks. By allowing the Force to flow throughout their body, they could overcome their physical limitations (including old age, as was the case with Master Yoda), and allowed them to perform amazing feats of acrobatics, such as somersaults and backflips, not only for attack, but also to evade the attacks and strikes of their opponents.
Those who used Form IV could move at amazing speeds and could rain strong blows, jumping and attacking through the air. Powerful and lightning-fast spinning attacks could be utilized from all angles, either from ground or air.
A master in Ataru combat could appear like a blur to their opponents, attacking from all directions—from the front, the sides, overhead, or behind. The Force not only allowed them to perform amazing athletic feats, but it also helped guide their actions and movements in combat.
This form was also probably not effective for prolonged combat, as the nature of Ataru could greatly tax the body. Fatigue may have been the chief reason that Qui-Gon Jinn was defeated by Darth Maul, though his old age may have also played an important role in his fatigue. Another possible cause of Qui-Gon's death at the hands of Maul was the requirement of open space for the kinetic acrobatics of Ataru. Without ample space in the Theed Palace reactor core to move in, Qui-Gon was deprived of the key element in his defense, and thus could only attempt to block Maul's lightning fast barrage of Juyo strikes. This event had a profound effect on Kenobi—after his master's death, he decided to perfect his practice of Soresu, the most defensive of all forms.
Nevertheless, Ataru proved to be an effective combat form when used properly. Jedi skilled in Ataru fought with amazing grace and eye-blurring speed, using Force-assisted acrobatics and maneuvers to attack their opponents with powerful swings and offensive flourishes, never staying in one place long enough for their opponents to mount a proper counterattack.
Form V: Shien/Djem So, or The Perseverance Form was the fifth form of the seven forms recognized as canon by the last Jedi Council for lightsaber combat.
"I prefer more straightforward methods."
—Anakin Skywalker.
"Master of understatement."
—Obi-Wan Kenobi
Form V or the Way of the Krayt Dragon was a powerful style developed by Form III practitioners that preferred a more offensive style, since the defensive nature of Form III often led to dangerously prolonged combat. Djem So evolved into a combat style by combining the defensive maneuvers of Soresu with the more aggressive philosophy and tactics of Makashi.
Form V came into existence by taking the defensive skills derived from Form III and quickly channeling it into offense. A common example used to illustrate the difference was that that while Form III combatants effortlessly deflected blaster bolts, Form V practitioners excelled at redirecting the blaster fire back toward the opponent. This action simultaneously defended the user and efficiently injured the enemy. Form V emphasized strength and power over opponents. Many Jedi disapproved of this philosophy. Some in the Order may have felt that this lightsaber form led too quickly to violence, instead of diplomacy when dealing with disputes, because it appeared to call for the physical domination of an opponent, which was counter to Jedi beliefs.
Form VI: Niman was the sixth form of the seven forms of lightsaber combat.
"For superior balance, use the Niman form. This form has no specific strengths, but no weaknesses either."
—Kavar
The Way of the Rancor or The Moderation Form, Form VI was the standard style at and around the time period of the Clone Wars and the Great Jedi Purge. This combat discipline was often called the "Diplomat's Form." Unfortunately, all of the Form VI practitioners at the Battle of Geonosis were killed. As a result, full masters of other lightsaber forms sometimes considered Form VI to be insufficiently demanding.
Form VI attempted to balance all elements of lightsaber combat, combining the Forms that came before into a less intensely demanding combat style. The result was that the users' skill in each individual area of lightsaber combat was relatively moderate—they did not excel in any one area. Due to its "jack-of-all-trades" nature, the success of this form is largely dependent on the practitioner's intuition, improvisation, and creativity in combat rather than the rote responses derived from other forms. This broad generalization made Form VI well suited for diplomats, as they could spend their time training in the areas of politics and negotiation instead of combat training.
Form VI utilizes techniques from Form I, Form III, Form IV, and Form V.
Form VII: Juyo/Vaapad was the final form of the seven forms of lightsaber combat.
"I created Vaapad to answer my weakness: it channels my own darkness into a weapon of the light."
—Mace Windu to Obi-Wan Kenobi
Dubbed the Way of the Vornskr or The Ferocity Form, Juyo, a term from High Galactic, was originally considered an incomplete form for millennia. Generally viewed as undeveloped and rarely used by the Jedi and the Sith, Juyo was not seen as one of the main forms for generations of Jedi.
The most challenging and demanding of all forms, Form VII required intense focus, a high degree of skill, and mastery of other forms. Only two Jedi ever mastered Vaapad fully: Mace Windu and Depa Billaba. Intrepid, somewhat direct movements were used in combination with advanced techniques involving Force-powered jumps and motions. Form VII did not appear as fancy as Form IV, as there were not moves like twirling and flipping, but the technical requirements were much higher. Vaapad used seemingly free-wheeling and open movements, but with utter control on the part of the wielder. The end result, if practiced correctly, was a very unpredictable lightsaber style. The staccato swings and flow of the form made it seem as if the attacks were not linked—but in reality, it was merely confusing the opponent.
Form VII demanded the emotional and physical intensity of Form V, but it much more effectively controlled it—if mastered. Form VII, when fully mastered, resulted in extraordinary power.
However, Vaapad bordered on the edge of falling to the dark side, as it channelled one's enjoyment of fighting into the attack. Only Windu's mastery and concentration on the light side prevented him from succumbing to his own anger, which is why Vaapad was rarely practiced and very dangerous. As noted above, the only other known practitioners of Vaapad, Sora Bulq and Depa Billaba both fell to the dark side of the Force. Darth Maul, a Sith Lord who appeared to have mastered Juyo, was so immersed in the dark side, yet so much in control of his anger that he could employ his own deadly variant of Juyo without fear. Coupled with his martial prowess, Darth Maul used this variant to defeat several skilled Jedi, including Master Qui-Gon Jinn. However, Darth Maul only devoted to the Form's physical focus, thus he remained silent during the duels on Tatooine and Naboo. Maul desired pure physical victory, rather than the "higher" Sith tradition of Dun Möch, which could dominate the opponent's spirit through taunts that expose inner doubts and weaknesses.
With that said, Vaapad was not just a fighting style. It was a state of mind and a power. The state of mind required that a user of Vaapad allow himself to enjoy the fight. He had to give himself over to the thrill of battle, the rush of winning. Vaapad was a path that led through the penumbra of the dark side. The power of Vaapad was simple: it was a channel for one's inner darkness; and it was a reflecting device. With strict control, a Jedi's own emotions and inner darkness could be changed into a weapon of the light.
Vaapad was also described as "a superconducting loop," with the user on one end and the opponent on the other. It was able to take the powers of the opponent and reflect it back at them. In his fight with Palpatine, Mace Windu used the Chancellor's own speed and hatred against him, reflecting it back against the Sith Lord and using it as his own power. Also, when Palpatine unleashed his Force lightning on Mace, the Jedi was able to use his lightsaber, with the power of Vaapad, to reflect the lightning back at him. However, because Palpatine was probably a master of the Sith variant of Juyo as well, he fed the power of Force lightning with his own pain, thus intensified the energetic attack despite his suffering.
The power of Vaapad was quite incredible: it was at once a form of lightsaber combat, a state of mind, and an actual tangible power. To use it required great mastery, discipline and, above all else, purity of heart and spirit. Vaapad users were intense, focused and introverted. There were even signs of pent-up hostility in them.
Around the time of the Jedi Civil War, Juyo was already the lightsaber form relied upon by the greatest of the Jedi, including the famed Jedi Weapon Master Kavar, indicating that Juyo was indeed a complete and effective form for millennia before Mace Windu created his version of Form VII, Vaapad, although it was also possible that the ancient Juyo masters and their skills became the casualties of war."