As game developers strive to have large, continuous, detailed environments in games, the memory limitations of computers and consoles constrain the amount of game assets that can be loaded into the game at a time. To get around this limitation developers can either section the game into levels or "maps" in which when the player arrives at the edge/end of a map, a new map loads which prompts a loading screen in which the player will have to wait for the new area to loaded into the memory. This can break the flow of gameplay of action-oriented games.
To avoid this pitfall, developers design their games to constantly load new assets from the disc as the player moves around the game environment, the closer an object is to the player the higher Level of Detail (LOD) is loaded. Using this method can eliminate loading screens from occurring (besides from when the game starts up) during gameplay.