The Office is a mockumentary. The primary vehicle for the show is that a camera crew has decided to film Dunder Mifflin and its employees, seemingly around the clock. The presence of the camera is acknowledged by the characters, especially Michael Scott, who enthusiastically participates in the filming.The main action of the show is supplemented with talking-head interviews or "confessionals", with the characters speaking one on one with the camera crew about the day's events. Sometimes two characters share an interview, speaking with each other and the camera at the same time.

Source: Wikipedia.org