Groups are an incredibly important feature within CiviCRM. In addition to their fundamental use as collections of contacts that have something in common, they play a critical role in CiviMail. Well-defined groups are one of the most important tools available when segmenting your CiviCRM contact database.

There are two kinds of Groups - Regular Groups and Smart Groups.

• Regular Groups allows you to manually place contacts into a group. You can then easily send emails to each person who is a member of the group without having to search through CiviCRM and select each member individually for the mailing.
• Smart Groups are automatically populated groups that are configured to include contacts that share a certain set of characteristics or activities. As contacts are added or edited, CiviCRM automatically checks them and adds them to Smart Groups if they meet the characteristics that you have configured.