A music genre.
Classic rock was originally conceived as a radio station programming format which developed from the album-oriented rock (AOR) format in the early 1980s. In the United States, this rock music format now features a large playlist of songs ranging from the 1960s and 1970s. Classic rock production ceased on December 31, 1979 with the transition into 1980s Hair Metal. Some stations continue to include a limited number of current releases.
The classic rock stations re-create the sound of album oriented rock stations of the 60s-70s (although usually with a much more limited playlist) and appeal mainly to adults, rather than teenagers. Some classic-rock stations also play a limited number of current releases which are stylistically consistent with the station's sound, or from established classic rock artists that are still producing new albums.
Classic rock in recent years has been expanded to include glam metal and progressive rock acts. These artists are often put on "late classic rock" stations (such as XM Classic Rewind) while the more traditional artists are put on "early classic rock" stations (such as XM Classic Vinyl).
A format that plays both classic rock and more current and modern selections is known as active rock.