Constraint satisfaction

Constraint satisfaction is like playing a game with rules. The game starts by giving you a bunch of pieces and a set of rules. You have to figure out a way to make all the pieces fit together so that all the rules are met. For example, if you were playing a jigsaw puzzle, the pieces would be the jigsaw pieces and the rules would be that all the edges of the puzzle have to match up perfectly. To solve the puzzle, you would move the pieces around until they all fit together in a way which matches the rules.