Pop can have different meanings. It depends on the people you ask. There's no general accepted meaning for that word.
Just see here: https://answers.yahoo.com/question/index?qid=20081025202031AA7Fzvt and http://english.stackexchange.com/questions/219990/what-does-mainstream-pop-music-mean-and-is-it-singular-or-plural
Haha, I totally didn't research that just to defend myself xD
I'm so convinced coz I know I'm right at this one