Well, honestly I know very little about any other painting medium so while I can answer questions about silk painting, I can't really compare it to others.

I guess the main differences would be that you have to tension the sheet to be able to paint it (in my case using a trampoline looking affair with rubber bands and safety pins), and the dye 'runs' as you paint with it, it spreads out quite a bit so you can't really do brush stroke textures, or go over painted bits with other paint to create depth, or anything like that.
Instead you use a black goop called "Gutta" to make a barrier that the dye won't pass, and then it's basically like paint by numbers, filling up each section that you've outlined. The 'stained glass' type effect is the easiest way to see this: Blocks of bordered colour, rather than being able to do shading or the like.