Community is the smallest district and the one the town would most like to grow: a group's own site, rather than a product people use — a football club, a makerspace, a nonprofit, a residents' association, a cause, a municipality. The distinction from social is that a community site belongs to a group; a social site is a product a group happens to use.
A square here costs a dollar, once, and the eviction rule that makes the commercial districts lively rarely touches this one — nobody pays a dollar to evict a choir. Square Town for communities is the invitation.
If your group's site is here on a seeded square, open it in town and pick up the keys.