Relationships in White Cup CRM are just that -- how different records are related to one another. Relationships are used to link ship to customers to a bill to account, and they're also how contacts, opportunities, quotes, and other items are linked to their proper accounts and other items.
Relationships are one-to-many, meaning a record can be related to as many other items as needed. For example, take a contact. Many times you work with the same contact at many ship to accounts and sometimes at the bill to account level as well. In White Cup CRM, you can have one record for that contact and have relationships between the contact and as many accounts as needed. This flexibility lets you have cleaner data (no need to duplicate your contacts!) while still maintaining good, accurate records.