An article on what constitutes a Community of Practice:

Communities of practice (CoP) have been hailed as the perfect vehicle for knowledge transfer and competence development, and the associated theory presented as a bridge between the theories of organisational learning and organisational performance (Snyder: 1997). Unlike some 'here today-gone tomorrow' solutions to corporate under-performance, such as business process reengineering or core- competency, CoP theory appears to have had a much longer period of maturation, finally coming to prominence as a result of its co-evolution with the theory and practices of knowledge management, especially the development of computer enabled and mediated networking. It has gained considerable currency in the field of corporate development because of the emphasis that is now placed on knowledge as a competitive asset. With its wider diffusion has come a proliferation of community types, such as, communities of interest, virtual communities, and distributed communities of practice, all of which, it could be argued, have diluted and even distorted the original concept. This may be due in part to the fuzziness of the original definition and the difficulty some may have of distinguishing a CoP from a team, a learning organisation, or some form of informal social group.

...via elearningpost