Where and why to use PEB\TEB?

Question

C++ / C#

Hello.
I read the topic on Habré: https://habr.com/ru/post/187226/
Working with PEB and TEB
But I didn’t quite understand why this is? Where is it used? I make software, I make money on forums, but I have never used it, and I didn’t even know what it was before ...
PS: Can I use simple words?)

Answer 1

TEB is used for at least SEH and TLS. Fibers are again in TEB.
CHANGED: by mistake first wrote TLB instead of TLS.