c# - struct - what is it for?

I know something about struct type. But I can't understand: what is it for? when have I use it? Classes, simple value-types and enums - that's all that I need.

Any suggestions?

UPD: PLEASE! Don't tell me that struct is in the stack (I know this :). What struct is for?

Answer

You choose a struct if you want value-type semantics. You choose a class if you want reference-type semantics. All other concerns are secondary to this one.