3. Show or Film?

I was reading to Onur's blog and he was talking about a reality show that is about another reality show. You can read that blog from here. That and made me think about what is reality show. Is a reality show still a reality show when everyone knows the things are done there not real? If the people are acting in those shows, what makes them different then Jim Carrey? Since most reality shows are scam and role playing then Truman Show was a reality show too. I just got confused myself could you help me please?