Gaming Licence Interview! help!?

0k so I am on the hiring process to working at a Casino in California. I have an appointment next week to get my background check, drug test and gaming licence interview. I dont have a bad record at all nor do i do drugs. I just dont know what a gaming licence is? What do they ask in the interview? What do they check? How should I dress! (Female) . Im literally freaking out about it. They make it sound so crazy and scary. Why do I need one anyway! -Help!?