Free shaping! Really quite simple. You wait for the dog to offer something, very insignificant at first, even if it's by accident, towards the ultimate goal. You mark/treat and wait for just a little higher of criteria next, etc. etc. until the dog is doing the thing you want.
For easy of imagination, if I wanted my dog to go to the front door and stand there next to it, I would first click/treat for a glance or step (whichever he happened to offer first) towards the door. Then I'd click/treat for a step, or numerous steps towards the door. Etc. etc. until I'm clicking for standing against the door. I just raise my criteria between each reward towards the ultimate goal.
eta; A lot of people like free shaping more because you don't have to fade the lure and it's harder on the dog's brain, resulting in more mental work/making them more tired. It's also fun to have a dog that is actively engaged in trying to learn for you/the reward and watching the gears turn so that they are more of a "thinking" dog instead of a dog following your cues. They learn to problem solve, basically, which is intriguing.
I can understand that. I did watch some video today. They act like its easy. But, is one better than the other? Lure or FS? Will one hurt my dog? That's important to me.