Final Fantasy Tactics was a very popular Strategy RPG for the PlayStation. It is credited for popularizing the Tactics sub-sub-genre, although contrary to popular belief, it was not the first Tactics-style game. A SNES game, Tactics Ogre: Let Us Cling Together was the first tactics RPG, though it was not released outside of Japan at the time, until it was ported to the PlayStation years later. The PlayStation port came out after Final Fantasy Tactics. Most of the same team that worked on Tactics Ogre: Let Us Cling Together worked on this game as well.
Final Fantasy Tactics is mostly lauded for it's complicated, dark storyline and deep strategy gameplay.