Matching Contacts is a new feature to help you control Update Duplicates on Import.
Choose a matching setting based on what information you have in the import and in your Contacts, and Big Business will match and update the right ones automatically.
For example, Contacts used as ShipTo's have an Shipping Address 1 entry at the least. Or, you might have Contact Codes or be using Ship ID 1 for your customers' id codes.