Actually if u take it literally rap is just rhyming. So basically hiphop is the style of music we all love and rap is just spittin lyrics. But you can also rap on a rock track so rap is not exclusive to hiphop.

Rap is not a music style by itself. You can't say 50 cent makes rap music and KRS-one makes hiphop. They all make hiphop. Because that's their style of music.