Depending on the type of a marketing action, you can use different descriptions for contacts in these actions. Whether they are internal (agents), organizational, or other contacts or attendees depends on the definition of the marketing action, however, they are always assignments from the contact management. The Attendees tab (formerly "External Contacts") contains a list of all attendees of a marketing action. This means that, in addition to external contacts, internal contacts can also be added, e.g. for internal training courses.