A "pop top" is the aluminum ring attached a strip of aluminum which is a part of the top of a beverage can. Pop tops were a huge innovation, eliminating the need for people to carry church keys. You pull the ring, which rips out the metal strip, leaving an opening through which the beverage may be ingested. Since their introduction, pop tops have been redesigned so that they do not actually detach from the can, thus eliminating the problem of pop top litter.