Seller carry back strategy

[James Wheelock]

I just watched a Robert Kiyosaki video where he was discussing investing with little to no money down for younger couples. He mentioned the strategy where you find a deal and structure it with an 80% mortgage and have the owner carry back the other 20%. Then he went on to say that it was a no money down deal. How does this work? Wouldn't the buyer still have to come up with a down payment on the 80% mortgage? Any help in understanding this would be awesome!