Short answers, pulled from the story.
Final Fantasy X-2 follows Yuna as she forms the Gullwings sphere hunter group to find Tidus, who disappeared into the Farplane after the events of Final Fantasy X. The story takes place two years after the original game during the Eternal Calm, where Yuna and her companions Rikku and Paine travel Spira to uncover the truth about Tidus and stop the machina weapon Vegnagun from destroying the world.
Final Fantasy X-2 was released in 2003 in Japan shortly before the merger between Square and Enix. An expanded version titled Final Fantasy X-2 International + Last Mission was released in 2004 for the PlayStation 2, and the game was later remastered for PlayStation 3, PlayStation Vita, PlayStation 4, PC, Nintendo Switch, and Xbox One between 2012 and 2019.
The three main playable characters in Final Fantasy X-2 are Yuna, Rikku, and Paine, who form the sphere hunter group called the Gullwings. Yuna is the High Summoner from the previous game, Rikku is her cousin and a member of the Al Bhed, and Paine is a new character designed to accommodate the game's action-adventure style.
Final Fantasy X-2 is set in Spira, a fictional world consisting of one large landmass divided into three subcontinents and surrounded by small tropical islands. The setting reflects an era of peace known as the Eternal Calm, where technology is embraced and the old religious order of Yevon is crumbling, featuring diverse climates from the tropical islands of Besaid and Kilika to the frigid areas of Macalania and Mt. Gagazet.
Final Fantasy X-2 received mixed reviews due to its tonal shift from the somber predecessor, the inclusion of numerous minigames, and the reuse of graphical designs from Final Fantasy X. Critics praised the innovative battle system and non-linear storytelling, while others found the missions too frivolous and the multiple outfits too revealing, though the game sold over 5.4 million copies worldwide on PlayStation 2.