The Avatar is the incarnation of the Spirit of the Planet in human form.
There is only one Avatar, who reincarnates himself through the centuries. Each time the Avatar dies it is reborn into the next nation. This successive cycle mirrors the order of the seasons:
Water Tribes - winter
Firebending's aggressive, vicious, and direct moves mirror fire's all-consuming nature. Like a predatory animal, a Firebender tracks his prey until it exposes a weakness, then charges in for the kill. In a fight, a Firebender makes up for his lack of defensive moves by overwhelming his opponent with a barrage of blows in a variety of shapes. A quick kick or jab produces a short range burst of flame, whirlwind kicks generate blazing arcs, punches throw compact fireballs, and a series of spinning kicks results in rings of fire exploding outwards in all directions. When several Firebenders combine their energy and attack as one, they are able to shoot missiles of flame at long range. As a fighting style, Firebending focuses on annihilating the opposition, much like the Fire Nation's political aim.
The Firebending forms use the martial arts style of Northern Shaolin.
The proud, strong spirit of the Earth Kingdom embodies Earthbending, which uses the ground as a weapon against an opponent. Exceptionally muscular, Earthbenders use their strength to overpower opponents. To throw an enemy off balance, an Earthbender physically strikes the ground with his hands or feet, causing localized earthquakes. To dodge an attack, an Earthbender uses the earth as a catapult to buck his body high into the air, and then upon returning to the ground, he softens the earth, easing his landing. Additional moves include creating fissures as traps for enemies to fall in, and raising slabs of stone for defense and offense. An Earthbender attacks by levitating stones and then propelling them at his enemy. Earthbenders also possess the ability to 'magnetize' their limbs to stone, allowing them to scale shear walls and cliffs. A high level maneuver reduces solid ground to quicksand, providing a pitfall for approaching enemies. Earthbending's most significant weakness is its inability to manipulate
man-altered metals. Firebenders exploit this weakness by smelting metal to remove its natural impurities, and then using it to construct their armor, ships, and forts.
The general Earthbending forms use the martial arts style of Hung Gar. However Toph's Earthbending uses the Southern Praying Mantis style.
Sandbenders are tribes of Earthbenders that moved into the Si Wong desert long ago, and have since adapted to the area and have mastered bending sand. Because sand is so much looser and shiftier than regular earth, it is not a simple transition for normal Earthbenders.
Sandbenders can use the sand to help keep them sturdy or stay rooted to the ground, and use it to whip up a small cyclone to power their sand-sailors, which they travel on. Toph was also able to turn the sand into solid ground so she could stand on it better.
The ability to bend metal is currently unique to only Toph. Even though metal is earth that has been purified and refined, it still contains trace amounts of earth inside of it. These amounts are too small for most Earthbenders to notice, but because Toph is able to see through Earthbending, she is able to find these natural properties and manipulate them through through the metal. After she gets the hang of this new skill, she can rip through metal like tissue paper, and mold it into new shapes.
Like the moon controlling the tides, Waterbenders use their chi to control the gravitational effect on water. In contrast to Fire and Earthbending, Waterbending's strength is its defensive capabilities. Waterbenders redirect the energy from an opponent's attack and use it against him. But Waterbending's intent is to control opponents, not to harm them. The style is evolved from ancient healing practices where the healer redirects energy paths in the body to cure an ailment.
A Waterbender's control of water in liquid, solid, and gas form offers him many defensive maneuvers. He may stop an attacker by encasing his feet in ice, or escape by creating a screen of steam for cover. In a fight, a Waterbender suspends a body of water around his fighting stance, and then lashes out with water whips and powerful waves. If there's no water at the scene of a fight, a Waterbender collects all the available moisture from the air and ground around him and concentrates it into an amount of suitable to attack and defend. As a backup, a Waterbender always carries a skin of water. While reliance on a water source is a significant weakness of the style, Waterbending at its highest skill level contains the most powerful technique among all the Bending Arts. At close ranges, an expert Waterbender uses an opponent's body against them. They harness the ample amount of water within the human body to control an opponent like a puppet master. The tendencies to control rather than destroy, and to heal
rather than harm, embody the humane and noble characteristics of the Water Tribes.
The Waterbending forms use the martial arts style of Tai Chi.
Because plants are so limited in the Southern and Northern poles where most Waterbenders live, this type of bending possibly originated with the Waterbenders that live in the Earth Kingdom swamps.
As seen by Huu in the Book: 2 episode "The Swamp", he was able to control vines by manipulating the water inside of them. This technique could make the vines like an extension of his hands, with enough power to grab and hold/throw people or use it as a full-body shield.
Airbending shares Waterbending's defensive nature and peaceful philosophies. However, it's versatility in practice and application makes Airbending the most dynamic of the Bending Arts. Airbending allows one person to defend against multiple attackers from different disciplines - ideal for Air Nomads traveling in foreign lands. An Airbender defends with blasts of wind, and then using a variety of wind-based counterattacks, knocks his opponent off his feet.
Airebenders are faster and more mobile than any other Bender. To confuse his enemy, an Airbender constantly circles him, rapidly changing direction to cleverly evade attacks. If an Airbender is struck, he absorbs the force by blowing his body back like a feather. While Airbenders cannot fly like Peter Pan, they use wind to enhance all of their normal movements. They can run faster by decreasing air resistance; jump higher and farther by creating wind gusts that lift them and allow them to float for a few seconds; slow a long decent by forming a wind cushion; and run up walls and trees by generating a current of wind. A high level attack involves creating a fierce air vortex that sucks in an opponent, rapidly spins him around, and then spits him back out onto the ground.
An Airbender's signature tool is his staff. Like all objects in Avatar, the staff does not possess any magical properties. However, it mechanically transforms into a small glider. To propel the glider, an Airbender controls air currents to sustain its flight over limited distances. In addition, small propeller blades extend from the top of the staff. Depending on the glider's orientation, it rockets forward or hovers vertically like a helicopter when an Airbender thrusts wind at its blades. In its untransformed state, an Airbender uses his staff as a weapon to enhance the amount and power of his attacks and defenses.
While Airbending is the most dynamic of the Bending Arts, it lacks a deadly finishing move. This fact reflects principles of the Air Nomads, which teach that all life is precious and conflict should be avoided whenever possible.
The Airbending forms use the martial arts style of Ba Gua.