How to make a game world that is procedurally generated.

I was wanting to make a large game world similar to the world in fuel but, it just takes up too much disc space. I read somewhere that they used some sort of algorithm for it but, of course I don’t know what it is, and I’m simply just not good enough at math to come up with something like that. I was wondering if some experienced programmer could help me out possibly? Thank you.

There are algorithm to develop the terrain and the world as you walk in. Meaning that before you got to a place, nothing exist and when you leave everything disappear.
The problem is that you want the same terrain and building when you come back or that will screw the gameplay.

My tip and it is only a tip because I have never tried nor implemented this:

use the position of the player and a hash function. Those return a value within a range that tends to be somewhat random to the user (not to the function). Then use the returned value to develop the relief of your terrain.

Store all buildings in an array and use the returned value from the hash function to pick one from it.

Again, this is more a lead than a solution, but that is where I would start. You can find plenty of hash functions online depending on what you wan to do. Avoid the security ones (MD-5, SHA) as you do not need that level of algorithm.

Finally, a game world is never endless. It only looks like because you can walk tens of km but there will come a time (I think when position gets around 10 000) when the engine will throw a warning and the game will start acting weird. This is when you reach the end of the float accuracy.