The idea here is that instead of making a player completely define the character upfront, you build the character as you go. For example, you don’t choose your Thief’s Moves in DW until you actually need one. Why would you want this? This can be great in oneshots in that it saves time up front, and also, it makes sure that the player won’t choose a move that they will never get to use!
I’ve seen this also used with Drives, Flags, etc. so that the game is not held up while a player thinks it through. Coming up with good ones can take a bit, so putting this off until it becomes relevant again helps keep things going.
What else have people seen work well? What hasn’t worked well?