Group Moderators are Members that can manage a Membergroup. Group moderators have access to the Moderation Center from where adding and removing members can be done. From the moderation centre group moderators can accept and decline requests to join the membergroup from (Profile > Group membership)

Please note that for a member to be able to request membership for a group, that group must be set to request in the membergroup settings.

Alltho being able to add and remove members, group moderators do not have the ability to change the groups name and online (or display) colour. These permissions stay souly with the Administrators.