Making a minor change to an existing product or service that pays huge dividends.
Some examples include adding sleeves to a blanket and calling it a "Snuggie" or designing ketchup bottles so they stand upside down keeping the ketchup consistently draining downward. And of course there are major innovations as well such as adding cameras, video capability, music, maps, Internet access, and games to cell phones.
An "inventor" creates completely (new) products.
An innovator comes up with a new way or better way of using what (already) exists!