Freemium, a portmanteau of the words "free" and "premium," is a pricing strategy by which a basic product or service is provided free of charge, but money (a premium) is charged for additional features, services, or virtual (online) or physical (offline) goods that expand the functionality of the free version of the software. This business model has been used in the software industry since the 1980s. A subset of this model used by the video game industry is called free-to-play.