Club groups can be used for what ever you need. It is an easy way to group members together for emailing and reporting etc.
You can add as many groups as you need and members can be in as many groups as you like.
Once you have added a group (Setup > Club Groups), to add a member to it view their account page and click on the "Groups" tab.
Click on the "Add Group" button and select the group to add to that member.