With contact groups you can easily organize your contacts, making it easier to email a specific set of people. 

Creating contact groups

  1. Click Gmail at the top-left corner of your Gmail page, then choose Contacts.
  2. Select contacts that you want to add to a group, click the Groups button. , then Create new.
  3. Enter the name of the group.
  4. Click OK.

Adding contacts to an existing contact group

  1. Select the contacts in the Contacts list.
  2. Click the Groups button. 
  3. Select the group you'd like to add the contact to, or select Create new to create a new group.
  4. If you have multiple addresses saved for a contact, you can choose which address should belong to the contact group by opening the contact and clicking the small arrow next to the group you'd like to modify.