A sense of community, from a psychological perspective, is the emotion people experience when they're part of a functional and healthy group. Many experts believe that this feeling is something that people crave, and when it isn't present, people may lapse into depression or suffer other problems. A sense of community can come from being part of any kind of group, from a church group to a town, or a social circle.
One of the fundamental aspects of a community is that there are generally barriers. The people in the community see themselves as separate in some way from others who aren't part of the group. Sometimes they can even make it very difficult for others to enter the community. These barriers could sometimes be subtle, like inside jokes between friends that make others feel excluded, or they could be more obvious, like rules that restrict membership to certain clubs. Even though barriers are often seen as a negative thing, many experts think they are essential to forming a real sense of community.
Mutual benefit is often another key aspect that helps build a sense of community. Personal gain is one of the primary motivating factors for joining a group, and everybody in any group generally wants to get something in return for their participation. On a larger scale, this could be something like jobs or food, and on a smaller scale, it might be social connections that provide beneficial relationships.
One of the things that usually really helps build a community is the personal connection people feel to the other members. They may have close friends in the group, and there is usually some kind of shared history. This gradually helps form a bond, and experts believe these bonds help create a sense of community.
When individuals become a part of a community, they usually expect to have some control over how things play out. Communities usually allow members to have some amount of influence on policies or choices. Sometimes this can be subtle, with some kind of hierarchy that limits individual powers, but in those cases, there is usually a path for rising in the ranks. According to some experts, if people don't feel that they can contribute to the choices made by the community, they might eventually begin to feel that they don't really belong, and this can cause the community to collapse.