I've never understood the difference. When I solve sudokus, including this one, I use backtracking all the time. "The 2 goes here or here, if it goes here then

I've never understood the difference. When I solve sudokus, including this one, I use backtracking all the time. "The 2 goes here or here, if it goes here then I get a 2 here, a 2 here and there's no room for the 6 there...so the 2 goes in the other spot after all". The "forward methods" are equivalent: just shortcuts to the same thing, spotting reusable patterns like the "ringing the domino" motif the solver identifies in the video.