This is a topic that I have been thinking about for an exceptionally long time. I'm sure I don't need to explain these kinds of music theory basics, so I'll skip right to the relevant stuff. In modern hip-hop, the rhythm section contains a bass drum and a snare. That isn't literal instrumentation, more of an ideology founded in popular music where the strong beat is felt on beats 2 and 4, while the weak beat is on 1 and 3.
The bass drum is consistently present in most modern songs. The snare, however, has taken on a life of its own with the addition of synthesized sounds.