This article is from the Training Your Dog FAQ, posted to rec.pets.dogs newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
There are several kinds of collars. There are the plain flat buckled ones for everyday use available in a wide variety of colors, sizes and fastners (from buckles to quick-release).
Note that puppies do not need corrective collars.
For training purposes, there are choke collars (also called training collars), pinch collars and prong collars. Used properly, there is nothing wrong with any of these collars, although they often look rather alarming. The point is that these collars are for control, not for pain infliction. Yanking savagely on these collars is counterproductive; firm corrections get the point across without injury. Try this experiment: wrap each of the collars around your arm in turn and have someone experienced with corrections give a correction to your arm.
To prevent your dog from injury from corrective collars, do not leave them on when you are not around. Its usual collar should be a plain flat buckled collar; save the choke and prong collars for actual training and when you are around.