My understanding is that an atheist is
someone who believes that there is no
god. An agnostic is someone who is
awaiting evidence, or who has not
decided that there is a god. Somebody
who does not go to church can be an
atheist, or an agnostic, or just
antireligeous. Oh and lets not forget just
unmotivated.

My current understanding of being
antireligeous is that of someone being
against the institution of perpetuation of a
faith, not of the faith.