What does a LODs do explain to me?

Now that there migrating to 4.14 pretty soon on, so I was going to make a guess on what are LODs since I don’t know about
are they

1.loading it up to a perfect texture
2. are they similar to source engine and stuff
3.do they load up models quality to make it perfect like Killing Floor 2 for example?

What do you people know about LODs or share a link about it? just trying my best to guess what it is?

also does LODs stand for something?
I wanted to search it up but I want to community to know what it is, or already know and I don’t

LoDs stand for level of detail, which basically means how detailed a model is. The more detailed, the more polygons it has, so more details = more resource usage. By using LoDs, you can change to a model with lower polygon count when you get further away from it, so you use less resources; since you’re further away from the model, you’re not going to be seeing those details anyway.

TL;DR: The further you move from things, the less detailed things get, so it uses less resources.