From PhpCOIN Documentation
Clients are the main reason for phpCOIN to exist, and the client tables are central to all other phpCOIN functions. Almost every function within phpCOIN can be disabled except "Clients"
In addition to the main client information record containing his or her username, password, join date and address info, another table can contain additional email addresses that the client uses. With password/username fields for the additional addresses, it could also be used to track assigned email addresses and logins for that client.
A client record can be created manually by an administrator, or automatically when a surfer places an order.
When a client record is deleted by an administrator, all other records that rely upon the client record such as helpdesk messages, domains, orders, and invoices for that particular client are also automatically deleted.