What makes a community?

Belonging to an online community myself, I don't think a physical aspect applies to having a community. The most prominent community I belong to is a musical fandom for a band hailing from England. It seems as though there are rules, but almost implied rules. The most structure the community I belong to is on the forum on the band's main webpage. There are moderators that make sure the message boards stay regulated. There is a "leader" in this community which also results in the community having common interests. There is a lot of reliability and knowing that other people in the community will be there for you. It's remarkable to think about just one, silly little band being able to unite people together like that. This community is very strong and I've only met one person in real life in this community- in yet I have many friends I've made. Some people may judge it from the outside- but they just really don't understand. And that's okay with me. They don't need to.

P.S. I posted about this topic on my tumblr blog and a ton of people from this community I belong to gave me their opinions. Very interesting. They reminded me that when we go to concerts when the band is on tour, that brings a physical aspect to the community. Even though we don't talk to all of them, their presence is just enough. Both the band and the community members/fans. There have also been many "meet ups" in this community (and others) where members from the same area gather in a certain area. Most of the communication I take part in in this community is on the website Tumblr.