This paper aims to provide readers with a useful introduction to Activity Theory, regardless of their field of study. Examples are given which include areas of research such as: information systems development, information systems in organizations, health care, and education. Activity Theory is a theoretical framework for the analysis and understanding of human interaction through their use of tools and artefacts. Activity Theory offers a holistic and contextual method of discovery that can be used to support qualitative and interpretative research. Activity Theory is particularly relevant in situations that have a significant historical and cultural context and where the participants, their purposes and their tools are in a process of rapid and constant change. The paper begins with an overview and background to the theory. Then, after explicating the practical value of its use, the paper concludes with a summary of some recent research which has used the method for analysis and discovery. The key concept of Activity Theory arises through an understanding of human consciousness as it has been shaped by experience and the subjectivity of human awareness.