With Google Groups, you can quickly use one email address to:
Send email to group members
Invite group members to meetings
Share content with group members, including Google documents, sites, videos, and calendars
These are particularly common ways to use Groups made for Email lists (as opposed to groups meant more for use as discussion forums). See What can I do with Groups to learn about different types of groups.
Send email to a group
To send an email message to a group, simply enter the group's address as a recipient in the To field of your Gmail Compose screen. If you start typing the address, it typically auto-completes in the field.
Note: each member of the list sees only the group's address in the message you send—they can't see the other members' names or addresses.
Send a calendar invitation to a group
To send a calendar invitation to a group, simply enter the group's address in the Guests field of your Google Calendar Create screen. If you start typing the address, it typically auto-completes in the field:
After adding the group, you'll see the list of members in the invitation on your calendar, if you have the appropriate permission to view the group's members list. The members appear as if you added them separately, and the group address itself no longer appears—for example:
Remember that anyone who receives the invitation can see the expanded members list.
Do you want to remove members from the invitation before sending it? Wait for the list of members to appear, and then click the X to the right of each name you want to omit.
Note: If you update the group (add members, delete members, etc.) after the Google Calendar invitation has been created, the invitation does not capture those changes. You’ll need to manually add or remove that member in the calendar invitation.
Collaborate with a group
With Google Groups, you can easily share your Google documents, sites, and calendars with multiple people. As you add new members to your groups, they'll automatically gain access to content you previously shared with that group.
For example, if you created a group with the address "firstname.lastname@example.org" and add 10 members, you can instantly share a Google document with them, just by sharing the document with the group's address:
If you later add another member to the group, that member will automatically inherit permission to access the document or any other content you shared with the group. Similarly, if you remove a member from a group, that individual will no longer have access to any content you shared with the group.