In its general charitable purposes, a community foundation is much like a private foundation. It typically makes grants in a variety of program areas, such as education, health, human needs, and arts, in a limited geographic area.
A community foundation's funds, however, are derived from many donors rather than a single source, as is usually the case with private foundations.
Further, community foundations are usually classified under the tax code as public charities and therefore are subject to different rules and regulations than those which govern private foundations. See http://en.wikipedia.org/wiki/Community_foundation for some additional descriptions.