The "Scarlet A" of the Out Campaign
Atheism is the lack of belief in a God, gods or any supernatural being, whatever claims are made for them, from creating thunder to creating the entire universe. Atheists tend to hold this view because of the lack of evidence for the existence of any of the hundreds of gods and goddesses that have been proposed to exist throughout history. The lack of belief in specifically religious deities, or a specific religious doctrine to go with them, is considered to be the default state for any human being.
Atheists are one of the most distrusted minority groups, particularly in the US. In many places, there are still laws restricting non-believers (such as from holding public office), even when equality on the basis of race or sexuality has been enshrined in law.