What does that mean [a completely non-destructive workflow in Substance Painter]?
TL;DRNon-destructive means painting through masks on fill layers rather than flat paint layers, so effects can be changed, reordered or removed later without redoing work.
So normally when you would paint, I can make a paint layer here, and then this would be actually I'm painting. But now if I'm like, oh, I don't like that, it's just a paint layer. So it's flat; I can't really do anything with that. But with something like this, you drop down a fill layer, add a mask, and now I'm actually doing all the work through a mask. So this paint layer is actually just flooding this with white, but the mask is actually driving where stuff can show up. So I have this, but then I can come in here, add a paint layer, drop that down, switch this to multiply. And because it's multiplying on nothing, it doesn't show up, but now I can start to bring in: no, I just want it to show up in these areas. And it's all about, like I said, non-destructive. So you can do so many things just back and forth with this. Like, oh, I don't like this paint layer, I can switch this on top and see what kind of results I get.