The series' opening sequence, offering a brief synopsis of the series.
Synopsis
The show follows Aang, a young airbender who was frozen in ice, and his friends as they try and stop the Fire Nation from dominating the world. Aang is actually the next avatar and in order for them to accomplish their goal, Aang must traverse the world and master bending all of the elements so that he will be ready to face Fire Lord Ozai. On his journey, he faces many difficulties such as discovering that he is the last remaining airbender and deciding between what is easy and what is right.
The elements
A crucial part of The Last Airbender's lore is the idea of the elements. In the series, there are four guiding elements that every nation is broken down into; the four elements are: fire, air, water, and earth. Each element has its own nation with its own culture and practices. For example, the waterbenders live at the poles of the world and are designed after Inuit culture.
Furthermore, certain people in each nation possess the ability to bend their element. This means that they are able to manipulate their element, such as shooting fire from their fists or lifting rocks without touching them.
The avatar
In the series, the avatar is a being who is capable of bending all four elements as opposed to just one. This person also has access to the spirit world and is able to communicate with them. He or she is tasked with using these incredible powers to uphold peace and balance of the world.
When an avatar dies, he or she is reborn in to the next element in the cycle (fire - air - water - earth) and this person can communicate with their past selves.
Aang the airbender
Aang is a (biologically) 12 year old airbender from the Southern Air Temple. Because of the impending war, Aang was told that he was the avatar and had to began his training earlier than normal; Aang was unable to cope with his responsibilites and ran off, only to end up almost drowning and being frozen in the water.
100 years later, he is awoken and tasked with mastering all four elements and restoring balance to the world. He often faces conflicts because of his youth but he utlimately succeeds on his journey.