In its most basic sense, a TV talk show involves a host who interviews a series of guests. The talk show is one of the oldest of TV genres, and some of today's talk shows still resemble the talk shows of TV's early days. Over the decades, however, the talk-show genre has splintered and evolved along several different tracks, so that now there are several distinct varieties of talk show. 314l

"The Tonight Show" on NBC has aired continuously since 1954, making it the longest-running talk show on TV. "The Tonight Show" is responsible for developing the format of the late-night talk show, which typically includes an opening monologue, interviews, musical performances and comedy skits. This format is still followed by most late-night talk shows, including those hosted by David Letterman, Jimmy Fallon and Jimmy Kimmel.

Early-morning talk shows are typically more news-oriented, although they traditionally also include interviews, musical performances and lifestyle features; "Today" and "Good Morning, America" are popular examples of this subgenre. Talk shows that air later in the day are less likely to delve into news or current events, instead focusing on celebrity interviews, lifestyle features and self-help topics; Oprah Winfrey and Ellen Degeneres have hosted immensely popular examples of this subgenre.

Politically-oriented talk shows on cable news networks - and on Sunday morning on broadcast networks - usually stay away from entertainment and lifestyle topics and stick to serious matters. Politically-oriented comedy talk shows, like "The Daily Show" or "The Colbert Report," however, bridge the gap between entertainment and political talk.