When atheists and theists debate the existence of gods, atheists generally ask for some sort of proof of the god or gods that the theist claims exist. Why do they do this? That is a difficult question to answer because while it is true that atheists often ask theists for proof that their god exists, sometimes they shouldn't. Asking for proof may end up confusing the important issues, causing distraction, and leading the conversation away from where it should be.
Read Article: Why Should Theists Prove that God Exists? Why Do Atheists Ask for Proof of God?