Concept
Volunteer source is normally used to indicate how you first acquired a volunteer for your organization. Recording that value when the volunteer is first entered lets you run reports later on to determine where you get your best volunteers in order to improve your recruitment efforts. A person may have only one volunteer source.
If you already have a section on your application asking how a volunteer found you, you would want the choices here to mirror those options.
Steps in this task
Someone who is not a volunteer is still allowed to have a volunteer source.
Deleting a volunteer source removes that volunteer source from all people who currently have it. All people who had that as their volunteer source will have no volunteer source once that source is deleted and changes are saved.