A time loop (or temporal loop) is a plot device in screen media and literature in which time runs normally for a set period then loops.
Most often the narrative is strongly impacted by the time loop; it is human nature to want to correct mistakes made or change the future. Characters may end up coming to a conclusion they would otherwise not have arrived at due to looping through a set time period repeatedly.
The most famous screen media example of a time loop is Harold Ramis' Groundhog Day in which Phil Connors (Bill Murray) finds himself waking up to the same day over and over.
Video games that have adopted time loops into their narrative include The Legend of Zelda: Majora's Mask (where the protagonist is aware of the loop, and can call on it at will) and Shadow of Memories (the protagonist dies at the beginning of the game, and must travel through time to various loops to prevent his death). In Final Fantasy, Garland is sent back 2000 years in the past where he became Chaos and sends the Four Fiends of the Elements forward in time by the same distance so they in turn could send him back in time. His theory was in 2000 years the time loop would close and he would no longer exist, therefore making him immortal.