What would the police ask during the polygraph test for a job?

[superkman2003]

I plan to become a police officer when I graduate, I was reading up on the "revised entry level letter" and I came across a part that said I would go through a polygraph examination. I am curious to what they might ask, I have done some things in the past that aren't pretty (nothing too big) and I am wondering if they are going to ask anything about my past, or just the present.