The document discusses the history and evolution of pop music from the 1920s to the present. It notes that pop music began being referred to in the 1920s and was used to describe popular music in Britain in the 1950s, incorporating rock and roll and new youth styles. Pop music was associated with artists like the Beatles and Rolling Stones in the early 1960s. The genre became more clearly defined and separated from rock in the late 1960s. Pop music is characterized as being commercially produced and appealing to wide audiences, in contrast to rock which aims for more authenticity. The document then provides examples of popular artists across different decades from the 1950s to 2000s.