Some of my best music lessons were around rhythm. Early on as a musician, I spent time playing reggae, with a bassist who wanted a guitarist, and was willing to put up with my innocence. He taught me a beat isn't an exact point in time, but rather sort of a region of probability, where sound is more or less likely to occur. Notes can begin or end at any point in a beat. The difference between reggae and ska is largely that in reggae, guitars and snare drum happen late in the beat, and in ska, it happens early. The former sounds languid, the latter frenetic. Same chords, same tempo, same "beat".

The other great lesson came from the jazz/rock drummer, Steve Smith. He describes "swing" as the simplest possible polyrhythm - a diminishment of three against two. Once you have three against two, you can start stripping out duplicates, until your down to ding ding da-ding ding da-ding ding... sound familiar? You get a strong backbeat (2 and 4), and an anticipation note at the very end of a bar before starting the next. Now, that anticipation note can be shifted earlier or later within its own beat, making things tighter or looser.

That's swing.