belief can mean a number of things: Belief in god is like having faith in god - can't see / feel it, but think / feel it is there.
Belief in oneself - to know that you are capable of doing something.
Belief that something can be done = confidence.
I do not believe in god as I do not feel that there is one, I have 't seen proof there-of.
I believe in myself, because I know myself, I am confident in what I can do and what I can accomplish.