Basically, it turns regular paint, like acrylics, into spray paint. You can supposedly use latex, varnish, and all kinds of other stuff.
You must thin the paint first. Too thin, it drips everywhere. Too thick, the spray clogs. It's an art I haven't yet mastered.
I'm finding it rather unpredictable, but fun.
Here I've started making a calendar.
Here is a close-up with multiple colors.