A-side and B-side originally referred to the two sides of 7 inch vinyl records on which singles were released beginning in the 1950s. The terms have come to refer to the types of song conventionally placed on each side of the record, with the A-side being the featured song (the one that the record producer hopes will receive radio airplay and become a "hit"), while the B-side, or flipside, is a secondary song that often does not appear on the artist's LP.

B-side songs may be released on the same record as a single to provide extra "value for money". There are several types of material commonly released in this way, including a different version (e.g., instrumental, a cappella, live, acoustic, remixed version or in another language/text), or, in a concept record, a song that does not fit into the story line.