What is a time loop?

Normally, a loop is a geometrical figure which, when traversed, results in getting back to the same point from where one started. A time loop, also known as temporal loop, is a common plot device in science fiction in which time runs normally for a set period, usually a day or maybe a few hours but then skips back to the starting point. When the time loop “resets”, the memories of most characters are also reset to the original’s space.