A retirement community, or active adult community, is a very broad, generic term that covers many varieties of housing for retirees and seniors - especially designed or geared for people who no longer work, or restricted to those over a certain age. It differs from a retirement home which is a single building or small complex where no "common areas" for socializing exist. Many retirement communities are planned for that purpose, and have special facilities catering to the needs and wants of retirees, including extensive amenities like clubhouses, swimming pools, arts and crafts, boating, trails, golf courses, active adult retail and on-site medical facilities. Other facilities have no or very few common amenities. An Age-restricted community generally requires at least one household resident to be 55 plus years of age or older (occasionally 50+ or 60+ years of age). Retirement communities are often built in warm climates, and are common in Arizona, California, Florida and Texas but are increasingly being built in and around major cities throughout the United States.

Naturally Occurring Retirement Communities (NORCs) can involve low-income residents receiving a richer mix of public services through a NORC model. They might serve people of all income levels who got together to furnish cost-effective transportation services. And there are NORCs for relatively affluent households that may charge $1,000 or even more in annual dues, and support paid and volunteer staffers who provide a rich variety of support services and cultural enrichment activities. NORCs can be very effective mechanisms to identify populations of people who need government-provided services and then provide those services in cost-effective ways[1]. An example would be Beacon Hill Village in Boston[2] provide support and resources for those who do not want to leave their current neighborhoods. Another term may be used for a predominantly senior citizen community, in which residence is unrestricted by age and job affiliation.

One categorization of retirement communities:

Continuing care retirement communities

The term Continuing Care Retirement Community is the primary term for a major part of the retirement scene, in books, magazines, accreditation and legislation, in parallel with the categorization just presented. A typical definition, from a New York Department of Health website is "Continuing care retirement communities(CCRCs) and fee-for-service continuing care retirement communities(FFSCCRCs) are residential alternatives for adults that offer, under one contract, an independent living unit (an apartment or cottage), residential amenities and access to a continuum of long term care services, as residents' health and social needs change over time." The accrediting agency CCRC/CARF uses the term CCRC with the same meaning. So do texts that include Senior Living Communities: Operations Management and Marketing for Assisted Living, Congregate, and Continuing Care Retirement Communities by Benjamin W. Pearce.