Pot calling the kettle black

Pot calling the kettle black means when someone accuses someone else of something they are guilty of themselves. It's like if you were playing games and one person kept saying another player was cheating, but it was actually the first person who was cheating. The saying comes from a picture of a black pot and a black kettle. People used to think that when the pot called the kettle "black" it was insulting, because they were both black!