Crank,
The only dumb question, is the one you do not ask!
The KMC missing link is designed to repair your chain after it has broken or if you need to disconnect your chain yourself to do your own repair work. A new chain usally comes with a spare repair link. The advantage of a Missing link is that it will work with all chains 21 & 24 Speed. (there is a different size Missing link for a 27 Speed.) This way if you are with a friend and he has a different brand chain than you, your link will work to fix his chain too.
We have a picture of them on our web site at
http://www.TaylorsBikeShop.com
Look in the shopping section under components in the little search window. They are cheep considering how easy they are to use.