Usefulness of layers

Hey guys
Am new to gdevelop, I just want to ask that what are layers used for and how are they used

you can show/hide layer ingame.
so good uses are runtime menus, world switches, UI elements, etc
you can also move cameras in different speeds on different layers, for background scrolling etc.

For practical development in the editor.
wh3en you have LOTS of stuff in your scene and just want to organize your objects, you can hide stuff, that youre not working on.

And then theres layer effects. you get some cool optical effects on layers, but they are expensive in performance, so its good to separate your objects that should be affected by those layer effects.

OK thanks for the reply
But how can I use it

Thanks a lot for that link, now i