The belief that a god or more than one god does not exist. Atheists believe in facts that are proven to be true and tend to lean toward science for answers. They believe things happen in the absolute literal sense and not in the spiritual sense.
Person 1: Why did bad things happen to good people?
Person 2: Bad things happen to everybody good and bad people. Even though it may seem like good people have worse luck bad people have just as bad. Which is why I believe in atheism
Person 3: I am Catholic so I believe the lord Jesus Christ is our savior and there is Heaven and Hell
Person 4: I don't believe in god but I accept your religion and will not make fun.
Person 3: Thank you and I accept your belief even though ignorant people of my religion may not accept your belief