Contacts can be thought of as profiles associated with your domains that provide required information such as your name, email address and phone number. Each domain has specific roles, including Registrant (the legal owner of the domain), Administrative, Technical and Billing. ICANN mandates that contact information be provided for each role. Using your Contact Manager, you can create/manage contact profiles which can be applied during new domain registration or modified at any time thereafter.
You can select 1 contact to be your default selection. The default selection is used to apply to all 4 roles mentioned above when you register/transfer a domain and do not select an order profile as part of that order.