This article aims to clarify the concept of context. Our motivation is the lack of consensus on what context is, despite common accept of the claim that learning is context-dependent to some degree, and despite a widespread interest in researching learning in specific contexts such as museums, classrooms, or workplace settings. We provide a minimal concept which is applicable to all references to context, properly construed. We point out that more general considerations of contextuality and compositionality must be reconciled and balanced out if the role of context in relation to learning is to be understood. We then flesh out the minimal concept with a typology of context categories relevant for understanding the significance of context for learning. The categories are "location," understood both in a physical-geographical and an institutional sense, "knowledge domain," "sequence of occurrences," "activity," "historical period," "social relationship," and "horizon of significance." We illustrate the usefulness of the typology through pointing out how it could help clarify discussions about transfer of knowledge and skills.