It refers to a special singing form of speaking rhythmically.

RAP is an important part of African American music, the main tone of street culture, and a piece of "black chocolate" in world pop music.

Singing and dancing rap is characterized by quickly telling a series of rhyming verses against the background of mechanical rhythmic sounds. One source of this form is the rapid, rhyming jargon used by radio presenters in the past when introducing records.