In Hip-Hop, the bass riffs and drum beats are often the main hook of a track. The bass drum is usually busier than in other styles, with different rhythms and the snare drum often strays from the 2 and 4 of pop.
It is very common for the drum and bass players to be either synthesized or looped, meaning that the musicians would record 2, 4, or 8 bars, and they would later be repeated in the song.
A disc-scratching DJ (turntablism), can also act as part of the "rhythm section," or they can act as a fill leading into the next verse/chorus, or they could be primarily part of the hook - the sky is the limit in Hip-Hop.
If a drummer is called upon to play for a whole song, rather than being looped, they usually try to sound like they are looped. Any fills that are done are usually without toms or cymbals, and are just a change in the snare, or fast bass drum notes.
Elements of other music styles have been introduced. For example, an artist called Guru is popular for fusing rap with jazz. Some other examples of this subgenre of Jazz-Rap are A Tribe Called Quest, Brand Nubian, Us3, MC Solaar, and the Roots.
Outkast often stylizes their songs with syncopated beats that swing, although they wouldn't be classified as Jazz-Rap.
Below are some common Hip-Hop drum beats. Although there are several subgenres of this style, the distincting is usually in the lyrical approach.