Photo by A. Davey (CC BY-NC-ND 2.0)

Tabletop games are typically structured as a series of one round after another until the game concludes. A video game’s main game loop similarly repeats over and over throughout the game in order to drive the game’s core mechanics. Many games are actually programmed using a main game loop, but even when that is not the case, it is still often useful for the game designer to use a conceptual model of a game loop.

Robert Nystrom’s Game Programming Patterns is a book that’s available in print as well as online (for free). It provides a great overview of what constitutes a game loop. Definitely recommended reading!