3 wire negative locks

I know this is probably a repeat question, but im not real sure on this. I have onboard relays for the door lock setup. I dont undertand what it means to have NO (normally open) or NC (norm. closed) ?? I have one of each for the unlock and lock. How do i know which one i use? Thanks ~Ed

if you are familiar with a regular spdt relay than this will be verry easy but i assume you are not. So here goes the normally open contact will be pin 87 of a normal relay, the normal closed will be pin 87a. Now what kind of car do you have an then i can put up a diagram if you need it .

2000 Grand prix. i have the Clifford AvantGuard 4. Also, if any of you are familiar with a MAS Window Roll-up Module, that would be great. I dont understand what the orange "acc. item" wire is and what the "activation" wire is. I wanna say that the activation is what im gonna hook the alarm output too, but then that still leaves orange "acc. wire" Thanks