According to The Hollywood Reporter, the Final Fantasy XIV TV show will involve an original story set in the world of Eorzea and that it will involve "the struggle between magic and technology in a quest to bring peace to a land in conflict."
Hivemind is the company behind The Expanse and the upcoming adaptation of The Witcher for Netflix. They will be the studio producing the show in conjunction with Square Enix and Sony. The show is still in the earliest stages of development and it likely won't be released for several years, which means that there are currently no details concerning the cast or storyline.
Final Fantasy XIV has a lot more potential for a TV show adaptation than most video games, due to its nature as an MMO. The character created by the player in Final Fantasy XIV is treated like the main character of any other video game, so it would be easy to switch them out with a character created specifically for the TV show and adapt the story from there. It's also easy to tell a story set around the events of the video game without stepping on canon, considering how big the setting is and the number of characters at play within the world.
There has already been one live-action TV show made about Final Fantasy XIV, known as Final Fantasy XIV: Dad of Light. Dad of Light told the story of a father and son in the real world who connect through the game, rather than taking place within Eorzea.
There have been several different Final Fantasy movies and TV shows over the years, but they were mostly animated projects. Final Fantasy: The Spirits Within was notable for such terrible reception that it almost destroyed the franchise forever while Final Fantasy VII: Advent Children was received better due to actually being related to a Final Fantasy game.
The Final Fantasy XIV TV show is currently in development.