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 new contact profiles.
You can use the Update Domain Contacts page to apply any of the contact profiles you created to your domains. Please keep in mind that applying contact profile changes will update the official records related to the roles for your domains.