afternoon  i like rap music
I am not a big fan but I know some stuff about it. It is a musical form that incorporates rhyme rhythmic speech and street vernacular.
i like it because of the rhythm to it, and the unique sound
Cool! It is very similar to spoken word poetry except rap adds music and the other doesn't.
so when did rap started?
I am not sure the very beginning but it definitely predates hip hop music. 
i guess there is a dividing line between rap and hip hop
Well are both very closely associated. There would be no hip hop without rap in it. It is the most basic ingredient. :)