The Groups application allows site members who share an interest in a certain topic or field to access related information and share their own experiences on a subsection of your website. Site users can create new groups or join already existing ones. Groups may contain their own page section, forums, message boards, media libraries, polls and projects and have the option of defining group roles. Groups can also be useful for managing access control.
Site administrators can manage groups of a given site through the administration interface. Learn more in Working with groups.
Both site administrators and users who are in authorized roles can edit the content and various settings of groups. Learn more about this in Editing groups. Further settings available only to global administrators are described in groups settings.
To allow users to use groups, you have to place some group web parts on your site. You can find the web parts in the Community web part category. An example of this that describes how to enable users to create groups can be found on the Allowing users to create groups page.