Atheism is the lack of belief in the existence of a god or gods. Atheism isn't a religion — it's just the opposite.
If you're fed up with religion or think that believing in God, heaven, and hell is silly, atheism just might be for you. An atheist doesn't believe in God or other supernatural beings. Some atheists state their belief more strongly, but it comes down to either "I don't believe in God" or "There is no God," which mean about the same thing. This is a stronger belief than agnosticism, which says we can't know if God exists.