In the last decade, the term “affordance,” coined by the ecological psychologist James Gibson (1986), has become a buzzword in CALL research. Often used to denote possibilities offered by technologies, the concept has been imported into CALL from cognate domains, such as human-computer Interaction (HCI). However, the CALL community has yet to engage in in-depth discussions on its meaning and usefulness for CALL research and design. The concept remains confusing, often misunderstood, and, at times, misused. This chapter provides an introduction to the concept of affordances, with a view to clarify its meaning and potential applications within CALL. Following a brief overview of Gibson’s theory of affordance, it presents and discusses leading HCI interpretations and conceptualizations of affordance that are particularly relevant to CALL researchers and designers. More specifically, it explicates HCI cognitivist and post-cognitivist views of affordances before exploring their relation to CALL affordances and their possible place within a CALL research agenda focusing more particularly on learner-computer interactions.