The document defines communities of practice as groups that share a passion or concern for something they do and want to improve at it. Communities of practice have three key characteristics - a domain of shared interest that distinguishes members, a community that engages in joint activities and helps each other, and a shared practice developed through sustained interaction. The document discusses how communities of practice relate to different organizations like education, where they can help ground learning in practice and connect students to real-world experience and lifelong learning beyond school.