It's a entertainment music. Pop is considered to be so, whatever style of music, the artists who create their music solely in public tastes and completely refrain from attempts to transfer some deeper values. Artists who were to officially admit, however, is few and the majority tries to add to their music, created by some kind of "ideology". It's a faction of rock music. As the "King of pop" is considered to be Michael Jackson, "Queen of pop" is Madonna, and "Princess of pop" is Britney Spears.