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, and on-site medical facilities. Others have some type of age restrictions but have few if any amenities (these generally don't fit into the "active adult" category). Still others are "Naturally Occurring Retirement Communities" (NORC), which become retirement oriented due to market forces rather than design. Another term may be used for a predominantly senior citizen community, in which residence is unrestricted by age and job affiliation.

There are really three broad categories of retirement communities:Fact: date=August 2008

• ACTIVE communities (all residential units, no longterm healthcare facilities)
• ACTIVE/SUPPORTIVE communities (a combination of residential and healthcare facilities - also known as "continuing care retirement communities" - CCRC)
• SUPPORTIVE communities (all longterm healthcare units, like assisted living and nursing care)

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 in cold climates too.

So far 6 U.S. states have created Certified Retirement Community programs with approximately 70 towns and communities included (see list). The obvious purpose of these programs is to encourage economic development - retirement, particularly baby boomer retirement - is very big business. States seek to encourage retirement in their states; keeping existing residents and encouraging out of state residents to move to a new state. Bill Haas of the University of North Carolina's Institute for the Future of Retirement estimates that the economic impact of a retiree household moving to a state is the equivalent of 1.4 factory jobs.Fact: date=October 2008

The six states that have publicized their certification programs are: - Texas - Louisiana - Mississippi - Kentucky - West Virginia(West Virginia calls its program a "Designated Retirement Community". -Tennessee has a program that promotes retirement in select communities in that state; the program is called "Retire Tennessee".

A number of publishers have created lists of the 100 best retirement communities or "100 best places (or towns) to retire" . For the most part these lists are helpful in terms of finding desirable communities to live in. One drawback to these lists is that these communities often become more expensive as a result of their popularity.