A community usually refers to a group of people who interact and share certain things as a group, but it can refer to various collections of organisms sharing an environment, plant or animal. This article focuses on human communities, in which intent, belief, resources, preferences, needs, risks and a number of other conditions may be present and common, affecting the identity of the participants and their degree of adhesion.

The word community comes from the Latin communis, meaning "common, public, shared by all or many." The Latin term "communitatus" from which the English word "community" comes, is comprised of three elements, "Com-" - a Latin prefix meaning with or together, "-Munis-" - ultimately Proto-Indo-European in origin, it has been suggested that it means "the changes or exchanges that link", and "-tatus" a Latin suffix suggesting diminutive, small, intimate or local.

German sociologist Ferdinand Tönnies presented a concise differentiation between the terms "community" and "society" . In his 1887 work, Gemeinschaft und Gesellschaft, Tönnies argued that "community" is perceived to be a tighter and more cohesive social entity within the context of the larger society, due to the presence of a "unity of will." He added that family and kinship were the perfect expressions of community, but that other shared characteristics, such as place or belief, could also result in gemeinschaft.

If the sense of community exists, both freedom and security exist as well. The community then takes on a life of its own, as people become free enough to share and secure enough to get along. The sense of connectedness and formation of social networks comprise what has become known as social capital.

Social capital is defined by Robert D. Putnam as "the collective value of all social networks (who people know) and the inclinations that arise from these networks to do things for each other." Social capital in action can be seen in groups of varying formality, including neighbors keeping an eye on each others' homes. However, as Putnam notes in Bowling Alone: The Collapse and Revival of American Community (2000), social capital has been falling in the United States. Putnam found that over the past 25 years, attendance at club meetings has fallen 58 percent, family dinners are down 33 percent, and having friends visit has fallen 45 percent.

Western cultures are thus said to be losing the spirit of community that once were found in institutions including churches and community centers. Sociologist Ray Oldenburg states in The Great Good Place that people need three places:
1) The home, 2) the workplace, and, 3) the community hangout or gathering place. With this philosophy in mind, many grassroots efforts such as The Project for Public Spaces are being started to create this "Third Place" in communities. They are taking form in independent bookstores, coffeehouses, local pubs and through many innovative means to create the social capital needed to foster the sense and spirit of community.

During human growth and maturation, people encounter sets of other individuals and experiences. Infants encounter first their immediate family, then extended family, and then local community (such as school and work). They thus develop individual and group identity through associations that connect them to life-long community experiences.

As people grow, they learn about and form perceptions of social structures. During this progression, they form personal and cultural values, a world view and attitudes toward the larger society. Gaining an understanding of group dynamics and how to "fit in" is part of socialization. Individuals develop interpersonal relationships and begin to make choices about whom to associate with and under what circumstances. During adolescence and adulthood, the individual tends to develop a more sophisticated identity, often taking on a role as a leader or follower in groups. If associated individuals develop the intent to give of themselves, and commit to the collective well-being of the group, they begin to acquire a sense of community.

Continuity of the connections between leaders, between leaders and followers, and among followers is vital to the strength of a community. Members individually hold the collective personality of the whole. With sustained connections and continued conversations, participants in communities develop emotional bonds, intellectual pathways, enhanced linguistic abilities, and even a higher capacity for critical thinking and problem-solving. It could be argued that successive and sustained contact with other people might help to remove some of the tension of isolation, due to alienation, thus opening creative avenues that would have otherwise remained impassible.

Community development is often formally conducted by universities or government agencies to improve the social well-being of local, regional and, sometimes, national communities. Less formal efforts, called community building or community organizing, seek to empower individuals and groups of people by providing them with the skills they need to effect change in their own communities. These skills often assist in building political power through the formation of large social groups working for a common agenda. Community development practitioners must understand both how to work with individuals and how to affect communities' positions within the context of larger social institutions.

Formal programs conducted by universities are often used to build a knowledge base to drive curricula in sociology and community studies. The General Social Survey from the National Opinion Research Center at the University of Chicago and the Saguaro Seminar at the John F. Kennedy School of Government at Harvard University are examples of national community development in the United States. In The United Kingdom, Oxford University has led in providing extensive research in the field through its Community Development Journal, used worldwide by sociologists and community development practitioners.

At the intersection between community development and community building are a number of programs and organizations with community development tools. One example of this is the program of the Asset Based Community Development Institute of Northwestern University. The institute makes available downloadable tools to assess community assets and make connections between non-profit groups and other organizations that can help in community building. The Institute focuses on helping communities develop by "mobilizing neighborhood assets" — building from the inside out rather than the outside in.