How Does Adjustment Layers> Layers Work In Ps?

Any links or tutorial you guys can show me? I don't exactly get how it works. Why is there a Red, green and blue ? What's that "Mountain-like" graph there for?

I really want to know how it works because how people uses it amaze me.

Thank you.

 

I think you are either refering to either curves or levels layer, they make your sig either bright, dark, contrasted thus to add additional depth and lighting... mess around with it and see for yourself

 

Exactly, if you don't understand, mess around with the settings and see what the end result is.