It means music that has a wide appeal, artists who sell massive singles, albums,merchandise.Commercial music is written to enhance the selling of a TV/Film scene or a product advertised on TV, Film or Radio. Tunes can be quite catchy to the ear so as to create a connection or memory with the product. Commercial music is any music genre that is into the mainstream, people from era of Michael Jackson refer to it as pop music too, (irrelevant) This is usually about hollywood industry, in india all commercial music is called Bollywood. Take case of Eminem, (Rapper) , J’Lo (Pop,Dance) , Martin Garrix (EDM) Pitbull (Rap) Skrillex (Dubstep) ,Avicii (Dance) Kygo (Dance) Everyone has these genres you can talk about it in more detail. So other than any kind of ROCK music where distorted guitar is not involved or some electronic sound is involved ,lyrics, and celebrity status persona and huge fan base to carry a commercial gains out of that music by concert or merchandise or what not is called commercial music. those are recognised by billboard charts also rock music is included but rock had always separate category to be recognised as commercial.