The kick and the sub-bass are both low-frequency elements. New listeners often blur them into one "bass" experience. Learning to hear them as separate things changes how you experience drum and bass.

The kick

A kick drum is a short impact sound. Hits, decays in under half a second, hits again. The energy is in the transient: the instant punch you feel in your chest. Kicks typically sit between 50 and 80 Hz with a click in the 2-3 kHz range.

The sub-bass

A sub-bass is a sustained tone. Plays a note that holds for one or two bars, then changes pitch. The energy is in the sustained low frequency: the weight you feel in your body for the full duration. Sub-bass typically sits between 30 and 60 Hz with no high-frequency content at all.

The interaction

Good DnB production sidechains the kick to the sub: every time the kick hits, the sub momentarily ducks out of the way, then comes back in. The two elements share frequency space without fighting. Once you can hear that ducking and recovery, you hear DnB at a different resolution.