Short answers, pulled from the story.
Yasumi Matsuno introduced the fictional continent Ivalice in 1997 as a request for a tactical role-playing game. This world became the most expansive setting in the history of the Final Fantasy franchise.
The inhabitants of Ivalice during the era of Final Fantasy XII include humans known as Humes, the rabbit-like Viera, the reptilian Bangaa, the pig-like Seeq, and the Nou Mu. These species also included the familiar Chocobos and Moogles alongside the magical Espers and Lucavi.
A catastrophic event struck Ivalice after the events of Final Fantasy XII and wiped out almost all of the non-Hume species. This disaster knocked the world back to a pre-industrial level and transformed it from a place of advanced magic and technology into a medieval landscape.
The Ivalice Alliance project began in 2006 following the departure of Yasumi Matsuno from Square Enix in 2005. This collection of games included titles such as Final Fantasy XII: Revenant Wings and Final Fantasy Tactics A2: Grimoire of the Rift.
The world of Ivalice was a direct inspiration for the design of Final Fantasy XIV with the scenario drawing direct inspiration from the setting. The Viera people from Ivalice became a player character option in Final Fantasy XIV.