Hip hop is the culture, which is made up of four elements: Breakdancing (b-boying), Emceeing, Deejaying and Grafitti.

Rap is the music that celebrates the hip hop culture, which is rhythmic speaking over beats.

Modern R&B is a derivitive of rap music, using sung vocals over hip hop beats.

Classic R&B is where it all originated from, including artists like Stevie Wonder, Marvin Gaye, Teddy Pendergrass, etc, etc....