A talk show or chat show is a television programming or radio programming genre in which one person discusses various topics put forth by a talk show host. Usually, guests consist of a group of people who are learned or who have great experience in relation to whatever issue is being discussed on the show for that episode. Other times, a single guest 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, etc. Sometimes, guests are already seated but are often introduced and enter from backstage. Gay Byrne, Steve Allen, Jack Paar, Johnny Carson, Dick Cavett, Ed Sullivan, Oprah Winfrey, Ellen Degeneres, Rush Limbaugh, and Mosunmola Abudu have hosted notable talk shows; in many cases, the shows have made their hosts famous.