This disk contains these final 6 episodes of the final season:
Chapter 16: The Southern Raiders - Prince Zuko and Katara take off on a private mission, to find the killer of Katara and Sokka's mother.
Chapter 17: The Ember Island Players - Prince Zuko takes the gang to his family island resort where they watch a theater representation of their history.
Chapter 18: Sozin's Comet Part 1: The Phoenix King - "Team Avatar" (Sokka's pet name for the group) prepares for a confrontation with the Fire Lord while Ozai assigns Azula a special honorable title - and crowns himself Supreme Ruler - with his own special title.
Chapter 19: Sozin's Comet Part 2: The Old Masters - Aang sets out alone to decide how to deal with the Fire Lord while the rest of the group set out to find Uncle Iroh.
Chapter 20: Sozin's Comet Part 3: Into the Inferno - Zuko and Katara pair up to face Azula in the Fire Nation, while Sokka, Zuki and Toph team up to stop Lord Ozai and his army from destroying the Earth Kingdom.
Chapter 21: Sozin's Comet Part 4: Avatar Aang - The Grande Finale, including Aang's final confrontation with the Fire Lord and Zuko's with his sister.
While I found Chapter 17 mostly missable, the final four chapters (18-21) run together like a full-length movie! All loose ends (that I could think of) get tied up nicely, including the fates of all the main and secondary characters.
An excellent way to end the entire series!