What's exactly is a server?

So I'm kind of a gamer, but I can't help to notice that video games like GTA V, Minecraft use a server when connecting to online. From my understanding, I think a server is like a giant supercomputer from different parts of the country that holds LOTS of space, weather it be a YouTube video, Facebook photos, etc. And that if I were to start say an online session on GTA C, the server would be capable of holding all of the information necessary to run the game online (the online 3D world, the missions, etc). So if I were to leave my car in Los Santos on the streets and drive to Sandy Shores and I come back to Los Santos, I should be able to find my car once again, since the GTA V servers have the whole game put online.

So is all that I'm saying true?

You might but since so much stuff is in a game they have clean by purging and deleting anything not in use

EX: You play fallout and kill a bunch of raiders and leave the bodies there come back in a few days they are either dead( and gone) or respawn. Nother one is when you see the game when you have to enter new places instead of just opening a door and your there lag my friend lag a choppy game is a bad one.

A server its like a ''room'' where you can play with other players online together. There are many servers out there for every game.