Short answers, pulled from the story.
The Compilation of Final Fantasy VII is a metaseries produced by Square Enix, consisting of video games, animated features, and short stories set in the world and continuity of Final Fantasy VII (1997). Its core products are three video games and one film, officially announced in 2003 with the reveal of Final Fantasy VII: Advent Children.
The Compilation of Final Fantasy VII was created by Yoshinori Kitase, director of the original Final Fantasy VII, and Tetsuya Nomura, its main character designer. Returning staff also included writer Kazushige Nojima, art director Yusuke Naora, and composer Nobuo Uematsu.
Kitase explained that Final Fantasy VII's ending left more development opportunities open for its characters and setting than other games in the series. There was also a financial incentive: following strong sales of Final Fantasy X-2, then-CEO Yoichi Wada saw an opportunity to tap fan demand for more of VII's story.
Before Crisis: Final Fantasy VII was never released in western markets. Mobile phones available in North America at the time of development could not support the game, and later the producer Kosei Ito left Square Enix in 2008 and Hajime Tabata moved to other projects, making localization unlikely.
Sales were strong for several titles. Advent Children sold 2.4 million copies worldwide through 2006 and four million by 2009. Final Fantasy VII Remake shipped and sold over 3.5 million copies within three days of its April 2020 launch, becoming the fastest-selling PS4 exclusive in history, and reached over 7 million units by September 2023.
The Compilation directly inspired the creation of Fabula Nova Crystallis Final Fantasy, a subseries linking multiple games through a shared mythos. The battle sequences in Advent Children also served as inspiration for Motomu Toriyama when designing the combat system for Final Fantasy XIII.