This document provides an overview of communities of practice by summarizing key definitions and the history of the concept. Communities of practice are informal groups that form around common interests or activities whose members learn from one another. They were first studied in apprenticeship contexts but the concept has since been applied to organizations. While communities of practice can enable knowledge sharing, their informal nature also means they may not always align with organizational goals. The document outlines debates around applying the concept to businesses and possibilities of virtual communities of practice with new technologies.