The A-side and B-side are the two sides of phonograph records and cassettes, and the terms have often been printed on the labels of two-sided music recordings. The A-side usually features a recording that its artist, producer, or record company intends to be the initial focus of promotional efforts and radio airplay, with the aim of it becoming a hit record. The B-side is a secondary recording that typically receives less attention, although some B-sides have been as successful as, or more so than, their A-sides.

A phonograph record, a vinyl record, or simply a record or vinyl is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The groove usually starts near the outside edge and ends near the center of the disc. The stored sound information is made audible by playing the record on a phonograph.