Permission Groups are the permission level that an admin should review if a user is able to view but not able to export a list of markers from Salesforce Maps. Permission Groups are used to grant access to features in Salesforce Maps, such as allowing marker exports, editing details tab fields, enabling weather tab, and so on1. The admin can edit existing permission groups or create new ones to assign different features to different users or profiles1. If a user is not able to export a list of markers from Salesforce Maps, it means that the user does not have the 'Allow Marker Exports' permission checked in the Permission Groups on Maps configuration page2. The admin can enable this permission for the user or profile by editing the corresponding permission group2.