The term affordance was coined by Gibson (1977, 1979) to define properties of objects that allow an actor to act upon them. Norman (1988) expanded on this concept and presented the concepts of real and perceptual affordances in his book The Psychology of Everyday Things. Norman was essentially the first to present the concept of affordance to the field of human-computer interaction (HCI). Since then, affordance as a term has been used by many designers and researchers. But as Norman (1999) explained, many of the uses of the term are vague or unclear, which prompted the writing of his 1999 article in the Interactions periodical. In fact, there have been many publications that try to elucidate the term (see Hartson, 2003; McGrenere & Ho, 2000). This article will try to provide a brief overview of the term and its many subclasses. It will try to give the reader a clear idea about what affordance is and how the concept can be used to allow designers and researchers to create better user interfaces and better interaction devices. The article however, does not try to clear up any ambiguities in the usage of the term in the literature or present a new way of viewing affordance. Rather, it tries to provide a short overview of the literature around affordance and guide the reader to a correct understanding of how to use affordance in HCI.