Again, lots of good ones. I thought eigenperson offered was the best explanation, and he's the winner. But I just want to note how hard it is to pick a winner, given that all of these posts kind of riff off each other. They work as a collective and picking out the best synthesis of all the info offered is a challenge. Will do another later this week.
A short documentary about Bruce Riley, an artist who paints abstract wonders with poured resin