The Shin Megami Tensei: Persona 3 FES is an enhanced version of the original game, known as "The Journey". This new chapter adds a story set after the events of the first game, with around 30 extra hours of gameplay. The storyline focuses on Aigis, one of the main characters.
The game also includes some other changes such as a "Hard" difficulty level, 23 new Personas that you can summon, the ability to fuse weapons, and changing the clothes of your characters.