From The TV IV
An establishing shot is a brief shot which appears at the beginning of a scene to indicate the location of the scene.
For example, an exterior shot of a building precedes a scene which the audience is meant to deduce takes place inside that building. In television, establishing shots become especially important because of the small number of location sets. They are most frequently used in multi-camera sitcoms, because such sitcoms are typically filmed on sound stages, and establishing shots are the best ways to imply exterior space on sets which truly have no exterior. The overwhelming majority of establishing shots in television are exterior shots, although not all—the interior shot of the North Hollywood Metro Red Line Station in Alias, which is where the agents hold their secret meetings in the early seasons, is a notable exception.
Because television establishing shots tend to be short pieces of stock footage which are used frequently throughout the series, many establishing shots become trademarks of their respective shows, and the locations portrayed become almost as famous as the characters. Examples of this would be the establishing shot of Central Perk on Friends or the exterior shot of Tom's Diner which opens many episodes of Seinfeld. In fact, establishing shots are so familiar to viewers and such a television convention that many shows have played around with the concept. The series Fawlty Towers, for example, used the establishing shot of the titular hotel as its title sequence in almost every episode, and it often changed the sign out front to work in an extra gag. The series Working also frequently played with the establishing shot of the Upton-Webber building by having, for instance, vultures circling it, or by using it in the fake ads for Upton-Webber.