Casting call at Blockbuster?

I was invited to a casting call/audition at Blockbuster. First of all, what is a casting call? How should I dress if I'm a male? Is it like a group interview; if so, how many people will be there? What should I expect from this interview? What kind of question will be ask and what kind of things will we do? How should I personally act in this situation? Please give me some other advices if there's anything else you know. Thank you