Audiences are created as part of the User Profiles service in SharePoint, and a user’s inclusion in an audience is defined by a set of rules that can combine membership in groups or user profile property comparisons.
Audience targeting is use to personalize content display including list or library items, navigation links, or Web Parts. Audience targeting is commonly used to filter news items on Portals. As an example, the Content By Query Web Part (CQWP) supports audience targeting when doing content aggregation.
***Since the Target Audiences field is not defined as a Site Column, the column cannot be added to a Content Type through the SharePoint User Interface
It allows your page to configure itself depending on who is viewing it. For instance you could use Target Audiences to:
§ Show an English language test to one set of people and a Spanish language one to another
§ Show an assessment only to approved people
§ Show a different survey to people depending on their context
§ Show an observational assessment only to instructors or monitors, and not show it to ordinary participants
§ Give different assessments to people in different departments
What to choose for Target Audience?
It’s easiest to choose audiences as SharePoint groups, distribution lists or security groups used in authentication
You can also define rules-based groups of people called global audiences, which gives potential of more sophisticated filtering.