With Google Groups, you can create online and email-based groups, engage in discussions, create a question and answer customer support group, and organize information about a specific subject.
With Google Groups, you can create online and email-based groups. To learn more about Google Groups view the document below.
Google Groups vs. Contacts
Google Groups support such things as a discussion group and Contacts are a way to store and organize information about the people you communicate with. View the recap on the difference between Google Contacts and Groups.
For even more information about using Google Groups, check out the Groups Help Center.