Exact constraint

An exact constraint is like a set of rules that tell you exactly how something has to move. It's like when you play a game with rules that tell you how you can move your game piece. If you have to move it a certain way or stay in a certain area, that's an exact constraint.

In real life, machines and tools have to move in certain ways too. Sometimes they have to be precise and exact, just like in a game. These machines and tools have parts that fit together in specific ways so they can move exactly as they're supposed to. If one part is too loose or too tight, the machine won't work right.

So, an exact constraint makes sure that everything moves exactly like it's supposed to. It's like a game with rules that keep everything in order.