How to load less graphics when not visible

Hello, I saw a video of tricks developers do in their game. And they said that they do cutscenes so they can unload the previous memory so the game can run better. And I just wanted to ask if someone know how to do that. And also I’ve heard about you can make graphics load less when player isn’t looking in that direction. I am really sorry for my English. I’ve been having problems with my computer so leave your ideas here and as soon as I fix my computer I will try them.
Thank you all so much!

Even just using ‘open level’ will switch from one level to another, and free the memory.

If you want something a bit slicker, then you need level streaming:

The engine by default will not draw anything that is not in the camera view.

Thank you, I fixed my computer a few days ago and I tried it, it works fine! Thank you!