The contact type field contains 5 mutually exclusive check boxes:
Client: The contact is a potential customer, a lead or a customer/client with whom the recruiter will provide services by way of providing suitably qualified candidates.
Candidate: The contact is a candidate who will be submitted to clients during the recruitment process with a view to a successful placement.
Client Candidate: The contact may be both a client and a candidate at the same time or may have transitioned from someone placed as a candidate who is now in a position to hire staff.
User: The contact is a colleague working for the same company running the application in-house. This contact should be linked to the same company as all other users.
Referee: The contact is acting as a referee to one or more candidates, and may therefore be a future client.