An atheist doesn't believe in the existence of god(s); a theist is the opposite and believes in the existence of god(s). The difference lies in lack of faith v. faith.
An agnostic believes it's not possible to be sure whether one or more gods exist.
Combinations are possibly; an agnostic theist believes in the existence of gods, but also thinks it's impossible to be sure.
There are also apathetic agnostics; they don't know nor care whether one or more gods exist. This usually seems to go with atheism.
I suppose there should also be a word like nontheists; those who have faith in the non-existence of gods.
An agnostic believes it's not possible to be sure whether one or more gods exist.
Combinations are possibly; an agnostic theist believes in the existence of gods, but also thinks it's impossible to be sure.
There are also apathetic agnostics; they don't know nor care whether one or more gods exist. This usually seems to go with atheism.
I suppose there should also be a word like nontheists; those who have faith in the non-existence of gods.