STL iterator

hello
I've tried to read headers related to STL iterators, but they're too hard for my quite low knowledge of C++.
That's what I am wondering about:
deferencing an iterator gives me the value it points to.
But an iterator is an instance of a class...or not?
How does that work?
I'm actually trying to implement an avl tree class and I want now to set up an iterator class, just to make practice.
So I'm curious about STL iterators' behaviour.
Thanks for any help

Ohh, I've just got that "*" is an operator... it's solved.
Sorry for the useless thread