Sort of like a
pompom, made of thin, durable rubber strands rather than yarn. Those strands make it easy for the
dextrously challenged to catch, and seem to disperse a surprising amount of kinetic energy on impact when thrown at, say, a window or person.
The Koosh was invented by Scott Stillinger, to help teach young kids how to catch. Adults can get plenty of enjoyment from the Koosh as well - it's an excellent worry-stone sort of toy. Cats are often fascinated with the texture and smell of the rubber.
Stillinger and his brother-in-law, Mark Button, started selling Kooshes under their company OddzOn Products in 1987, and cashed out in 1996. OddzOn is now owned by Hasbro.