Magento has many built-in customer data fields to support the order, fulfillment and customer management processes. However, every business is different and sometimes additional fields are needed. You can create and manage additional customer and address attributes as needed.
You can add custom attributes to the Account Information, Address Book, and Billing Information sections of the customer’s account. Customer address attributes can appear in the Billing Information section during checkout, or when guests register for an account. You can even create a special account page for guests to use when registering for a customer account.