Jewelry worn on the outside of the rectum, for show, cosmetic purposes only.
Generally a two piece item, where the more bulbous, thicker, end is worn internally, directly in the anus, similar to a butt plug. The more ornate piece, is left outside of the anus, though it can be worn inside.
The purpose is purely cosmetic.
To provide a more attractive view when one shows off their bare bottom, for show.
Practice (Associated Acts): Generally these are jewelry items attached to the end of an object, that is inserted securely into the anus, and is for show only.
It actually serves no sexual purpose, other than to be 'fashionable' in all parts of the body.
As it involves the use of a butt plug type of insertion object, care should be taken to not keep in place, for prolonged periods, as with Butt Plugs.
Properly fitted objects can pose no risk, but extreme sizes can cause a lessening of the elasticity of the sphincter muscles and inner muscles.
Noteworthy: Most pieces of anal jewelry are made from stainless steel, and contain some sort of gem setting in the portion that is visible to the naked eye.