Atheism is simply the opposite of theism. The prefix A means "without" or "not", so Atheism is simply a lack of belief in god(s). It is not a religion, just like theism is not a religion. Atheists are usually quite fond of life, since it is the only one we have.Theists if you think about it, need a god to make their existance make sense and to make them respect life.
That dog is an atheist. A new-born baby is an atheist. Most of the smartest people in the world are atheists. Coincidence?