Usually, guests consist of a group of people who are learned (such as current affairs experts or pundits) or who have experience with whatever issue is being discussed on the show for that episode. Other times, a single guest such as a celebrity or expert discusses their work or area of expertise with a host or co-hosts. A call-in show takes live phone calls from callers listening at home, in their cars, in their gardens, etc. Sometimes, guests are already seated but are often introduced and enter from backstage. There have been many notable talk show hosts; in many cases, the shows have made their hosts famous.