There are three main directions in hip-hop music: rap, hip-hop, beat-box. Hip-hop instrumental music consists of two main elements: rap (rhythmical recitative with clear rhymes) and rhythms given by the DJ (beat). Also there are many songs without vocals. Rap artists called MC.
One or more DJs programming rhythms on a drum-machine, sampling (use the fragments of other people's songs, especially parts of basses and synthesizers), manipulation of vinyl records and sometimes "beat-boxing" (vocal imitation of drum-machine rhythm).