In the record industry, a single is a song usually extracted from a current or upcoming album to promote said album. Singles are distributed through a number of ways; originally, they were packaged as "single" records with one or two other songs and sold before the release of the album. However, this practice has lessened as the Internet has made music more readily available to the public free of charge. Also, singles are commonly played on the radio, and with the advent of music videos in the 1980s, video versions of singles have become a common way of distributing the song to the public.   Wikipedia