A community is similar to a My Page in that it displays portlets. However, communities provide content and services to a group rather than to just an individual user.
You might create communities based on departments in your company. For example, the Marketing department might have a community containing press information, leads volumes, a trade show calendar, and so on. The Engineering department could have a separate community containing project milestones, regulatory compliance requirements, and technical specifications.
Each community is based on a community template, which consists of one or more page templates that can include portlets. Each page template you add to a community (either through the community template or through the community itself) appears as a link at the top of the community.
With the appropriate activity rights, you can create groups and portlets inside a community without affecting portal groups or portlets. For example, you might have a group that is responsible for maintaining schedules in a specific community without making that group a portal group. Or you may create a community links portlet inside a community for the convenience of community members.
Related Topics:
Community Pages (describes editing communities, adding pages, switching templates)
Bulk Add (describes subscribing multiple groups to communities)
Main Settings (Page) (describes creating community pages)