difference between chalk paint and flat paint
Now, flat paint is (usually) a latex paint that dries without a reflective finish-that's it-the finish is smoother (imho) than chalk paint. Chalk paint really dries quickly and it has a rough texture to it after it dries. Many people use wax or poly-acrylic sealant on top of their furniture piece to keep the paint from peeling. So there ya go, my best explanation.
You're going to get a LOT of responses for this. As far as I know and have read (and experienced first-hand), chalk paint is. any kind of paint that has an additive mixed into it to give it a gritty, matte finish and easy drying time. Many people use it because many times it negates the need for sanding a apiece and the finish allows for an easy time if you want to distress the wood.