Activity theory is a framework that analyzes human behavior in context. It views human activities as being composed of three levels - activities, actions, and operations. Activities are goal-directed and motivated. Actions are purposeful behaviors aimed at goals. Operations are automatic behaviors. Activity theory was developed by Soviet psychologists like Leontyev and Vygotsky who were interested in understanding human consciousness in social contexts using tools and artifacts. It looks at how subjects, objects, tools, rules, community, and division of labor interact within human activity systems. Modern activity theorists like Engstrom and Nardi apply it to fields like organizational learning and human-computer interaction.