What is the difference between a CAR and Standard ?

What does CAR stand for?

I am wanting to purchase an upper, and have a few questions.

Do I need to worry about the bolt hole sizes for getting my upper and lower to match?
I am getting a STAG lower.

If I get a CAR or Standard upper do I have to look for a special bolt, and bolt carrier to match it?

What I don't want to do is buy parts that won't work because I don't know any better.

thanks.

If you get a stag lower, both of those uppers will fit.

NO offense taken, haven't bought a thing yet.

Want to know the full scoop first!

thanks.

CAR--basically a AR carbine that sometimes looks like the old CAR-15s

CAR acronym: who knows....Colt Automatic Rifle (most prefered i believe), Colt/Commando AR, Compact AR, etc
its a cool name though....

no, for most ARs its standard hole sizes; h/w, some colts have different sizes than the rest

no special BCG needed--h/w, its best to keep used bolts w/ the bbls that were used w/ it, but not to worry
carbine buffers/springs are different sizes than the rifle length though

+1 on reading around more and trying the search feature