Pop Genre comes from the term popular, it is usually understood to be commercially recorded music, often oriented towards a youth market, usually consisting of relatively short, simple love songs.
This is taken from Wikipedia http://en.wikipedia.org/wiki/Pop_music

an aim of appealing to a general audience, rather than to a particular sub-culture or ideology
an emphasis on craftsmanship rather than formal "artistic" qualities
an emphasis on recording, production, and technology, over live performance
a tendency to reflect existing trends rather than progressive developments
much pop music is intended to encourage dancing, or it uses dance-oriented beats or rhythms
The main medium of pop music is the song, often between two and a half and three and a half minutes in length, generally marked by a consistent and noticeable rhythmic element, a mainstream style and a simple traditional structure. Common variants include the verse-chorus form and the thirty-two-bar form, with a focus on melodies and catchy hooks, and a chorus that contrasts melodically, rhythmically and harmonically with the verse. The beat and the

Harmony in pop music is often "that of classical European tonality, only more simple-minded." Clichés include the barbershop harmony (i.e. moving from a secondary dominant harmony to a dominant harmony, and then to the tonic) and blues scale-influenced harmony. "The influence of the circle-of-fifths paradigm has declined since the mid-1950s. The harmonic languages of rock and soul have moved away from the all-encompassing influence of the dominant function. ...There are other tendencies (perhaps also traceable to the use of a guitar as a composing instrument) – pedal- point harmonies, root motion by diatonic step, modal harmonic and melodic organization – that point away from functional tonality and toward a tonal sense that is less directional, more free-floating."