Distribution groups are mail objects in Exchange that send emails, or meeting requests, to multiple people without having to add all the email addresses individually.  Each individual member of a distribution group will receive their own copy of the email message. Additionally, distribution groups:

• Are identified by their naming convention of a period, a space, a unit designation, and a common name, i.e. “. EGADM Engineering Research – Management Information Systems (MIS)”
• Have a distinct icon in the Global Address List (GAL) which looks like two people:
• Can be reviewed and managed by users once created