Contacts are generated from Website Pro any time you send an email from the site. Website Pro extracts all addresses in the To, From, Reply-To, Cc, and Bcc fields. These end up in the Contact List in the Business App and are shared with Customer Voice (if applicable).
In Customer Voice, the Customers table will reflect the origin of the customer. If the customer is created from Website Pro, the Customers' table will show that.
Contacts can also be generated from Plugins, which will store all the details in the database of the server.
Example: Forminator Plugin.