No worries. Everyone starts out not knowing. The only dumb question is the one you don't ask.
There are gears in your transmission and then there are gears in your axles. The gears you are asking about are the ones in the axle.
I wrote up an explanation here that you may find useful: http://www.wranglerforum.com/f33/can...ml#post3598888
As far as finding out what you have, I have two fool proof methods of finding out. The first involves removing the differential cover and counting the teeth of the two gears. But that involves draining and replacing the fluid and making sure you get the cover sealed properly so it's not practical.
The second method is to raise either the front or rear axle off the ground completely (both tires). Make sure the other tires are secure so you don't roll and make sure you set the axle on a pair of jack stands since you need to get under the Jeep. Put the transmission or transfer case in neutral. Spin the drive shaft and make sure both tires are turning the same direction at the same speed. Then, count the number of times the driveshaft spins to get one full rotation of the tires. It's easiest if you mark a spot on the tires so you can see it clearly. If the drive shaft spins about 3-1/4 times you have 3.21 gears. If it spins about 3-3/4 times you have 3.73s.