What do atheists believe in?

My kid saw me reading this sub and asked me what atheism is. I told him it a word for people who don't believe in a god.

He understood then asked me what do atheists belive in, like evolution?

it got me thinking. there is no shared belief at all to be an atheists, right? just that we don't believe in any god/s...but we do all believe in evolution, right?