Fishblade2, What kind of shotguns do you have? Gauge, barrel length? Do you know if the chokes are fiixed or screw in? Do you want to know for hunting, home defense, or shotgun sport applications?
The 3 most common chokes are; improved cylinder, modified, and full.
Improved Clyinder- Close range, large pattern of shot, rifled slugs: Early season upland game, rabbits
(50% of the pellets will hit inside of a 30 inch circle at 40yds)
Modified- Medium range, Best all around choke: Late season upland game, general waterfowling
(60% at 40yds)
Full- Long range, tight pattern: Turkey, predator, pass shooting waterfowl
(70% at 40yds)
This is just the tip of the iceberg in the choke world. There are alot more situation specific chokes out there depending on what you are looking to do.
If you can provide more information, I will be glad to help you to choose a choke for the applications you will be encountering.