One drop — the roots-reggae drum feel named for what the kit leaves out: beat 1 is empty. The kick and the cross-stick (rim) land together on beat 3 only, the hi-hat ticks straight eighths, and that single "drop" in the middle of the bar is the whole groove. Everything else hangs off it: the guitar skank chops beats 2 and 4, the organ bubble fills the "an-a" of every beat with two short chords, and the bass plays long roots that lean on 1 and leave space around the drop.
Listen for how heavy beat 3 feels when nothing is on beat 1 — the bar seems to tip backwards. Mute the drums and the skank/bubble are just off-beats; add the drums back and the drop gives them a floor.
Practice: count "1 2 3 4" out loud, clap only the 3, then add the skank on 2 and 4 against it. Keep the bubble light — it is a texture, not a chord stab. Compare with rockers, where the kick fills all four beats.