Do you have a favorite community of practice for your passion(s) and career(s)?
In all cases, the key elements are:
The domain: members are brought together by a learning need they share (whether this shared learning need is explicit or not and whether learning is the motivation for their coming together or a by-product of it)
The community: their collective learning becomes a bond among them over time (experienced in various ways and thus not a source of homogeneity)
The practice: their interactions produce resources that affect their practice (whether they engage in actual practice together or separately)