system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is Grand Theft Auto 5 able to have such a large map, but little if any load screens?

Most games I've ever played have to load every time I enter a new area. How does Rockstar bypass this?
gpt
All of the map's data is available, but not always loaded.  Instead, the game loads only what is pertinent to the player and the information is left behind once it becomes irrelevant.  You can truly notice the effects of this when travelling very quickly across the map, such as in a plane or helicopter.  You'll notice structures start to appear on the horizon of your vision as the game loads them.  The faster you're travelling, the more abruptly these objects will appear to load, because you're giving the game less time to load them!  

This explains why many of your actions seem to be reversed if you leave an area for a little while and then return--what's happened is that the game has discarded the information from your last visit and has reloaded everything.  GTA V cannot be a truly persistent world for this reason.