Rhythm · chapter 1 of 11
A beat is a pattern in time
A bar of music is cut into sixteen equal steps, and four of them are beats: pads 1, 5, 9 and 13. The kick marks the beats, the snare answers on beats two and four, and the hats fill the gaps.
The playhead sweeps the pads from left to right, over and over. A lit pad plays when the playhead reaches it.
That is the idea.
Every drum beat you know is a handful of lit pads on a grid like this one.