Audiences allow you to target content to users based on their jobs or tasks in an organization. You can target content to users based on the values of properties that are contained in user profiles, the reporting structure of your organization, or Microsoft Active Directory directory service groups to which users belong.
Membership in audiences is determined by including the users in your organization that have properties that match audience rules, or are members of security groups or distribution lists that match audience rules. Since the rules or users that match them can change over time, audiences must be compiled regularly to determine current membership. Members of an audience see content targeted to that audience.