A group role helps you define how active you plan to be in the group. When you create a group, by default new members have the choice of being either an "Affiliate" of the group or a "Contributor/Participant."

Being an Affiliate means you want to keep track of the group and be connected to it, but don't expect to contribute or participate actively in the work of the group. An Affiliate member is more like an observer.

Being a Contributor/Participant means you want to play an active role in the group.

Some group leaders may choose to create custom roles for their groups. If a group was working on collaboratively developing a curriculum, for instance, they may want to have roles like Author, Editor, Fact-Checker, Graphic Designer, Subject Matter Expert, and Proofreader.
 

In addition, groups can use Roles on the Messages tab to better communicate with certain sub-sets of members performing certain functions within the group. You can send custom messages to a particular role rather than sending out blanket updates that may not apply to the entire group. You can also filter messages based on any roles you have chosen for yourself. See the Messages tab section of the Help Collection for more details.