By opening up or constricting.
Yes, they describe the various chokes.
Modified.
Chokes for shotguns shrink the bore's diameter to tighten the shot pattern and increase practical range.
they help with patterns of shot and accuracy of slugs
The choke on a shotgun "chokes" the end of the barrel, compressing your shot. Therefore creating a tighter pattern. Kind of like a nozzle on a hose. If you turn it on without a nozzle it will come out thick and not go very far, put a fine tipped nozzle on and the water will stay together and travel farther. Hope this helps.
It's called a choke, and restricts the bore a few hundredths of an inch. Most are round, for hunting, but there are some called "duckbills" that spread the shot laterally for combat purposes, though they're not popular anymore because they didn't offer a significant advantage. There are fixed chokes, permanently part of the barrel. There are adjustable chokes, which turn to constrict. There are removable chokes, which set in place with a wrench.
Depends on the choke. MOST chokes, including full choke, can safely fire slugs. Some makers of adjustable chokes recommend that slugs NOT be fired thru their chokes. A very few chokes, such as the Extra Full chokes used on some turkey guns should not be used for slugs.
A good basic article on chokes http://www.ssaa.org.au/stories/shotguns-a-beginners-guide-to-shotgun-chokes.html
Try e-gunparts.com
Refers to the amount of constriction at the muzzle.
Herter's sold various maker's products with their name on them.
Yes chokes are designed to tighten shot patterns.