Security groups : Use Security groups for granting permissions to gain access to resources. Sending an e-mail message to a group sends the message to all members of the group. Therefore security groups share the capabilities of distribution groups.
Distribution groups : Distribution groups are used for sending e-main messages to groups of users. You cannot grant permissions to distribution groups. Even though security groups have all the capabilities of distribution groups, distribution groups still requires, because some applications can only read distribution groups.
