A community is defined as a grouping of users by interest or skill set. For example, a “Pet Lovers" community would consist of users who have an interest in their pets, while a “Tech Support" community would consist of users who have the skills to provide technical support to an organization. A user can belong to any number of communities (NOTE: In previous versions of Liferay, communities were called groups). Communities are entities in and of themselves -- they do not belong to a specific organization or location.
A community contains a collection of pages. Each page consists of one or more portlets. Every community must have at least one page (represented by tabs) to be active, but there is no limit to how many pages it can have. Users can be assigned directly to a community or indirectly via an organization, location, or user group. User assignments will be discussed in a later section. Communities can either be open or closed. Open communities allow a user to join or leave them at any time without any type of approval from Administrators. Closed communities can only receive new users who are explicitly assigned by Administrators. These concepts will also be discussed in a later section.
Once a user has been assigned either directly or indirectly to a community, and assuming that community has at least one page defined, that user will see the community appear as an item in the My Places menu. By clicking on that menu item, the user will be taken to the selected community.
Communities are managed via the Communities Portlet. This portlet can be used to create, update, and delete communities; control the permissions of communities (including permission delegation); manage the pages of communities; assign users to communities (either directly or indirectly); and join or leave open communities. The pages of a community can either be managed via the Communities Portlet or by using the Add Content and Page Settings links. Examples of how all this works are provided in later sections.
As a general rule, objects in the portal can only belong to one community. For example, if a Message Board portlet is added to the "Support" community, all of the topics created through that portlet belong only to the "Support" community. There are only a few objects that don't belong to a single community such as organizations, locations, and user groups. These exception objects span all communities.