How does field mapping work in QuickBooks - Vtiger integration? 

For any synchronization to be successful, mapping fields between Vtiger and QuickBooks is necessary to ensure information is transferred mutually.

Take a look at the default field mapping for this integration.

Synchronization of Contacts
  
Vtiger to QuickBooks
The Display Name field is mandatory in QuickBooks. Hence the First Name and Last Name fields are combined and displayed as Display Name in QuickBooks.
QuickBooks to Vtiger

• The Last Name field is mandatory in Vtiger. If the Last Name field in QuickBooks is empty, the Display Name is taken as the Last Name in Vtiger CRM.
• If the Company field is empty, a default organization record QB Sync No Company is created, and a contact is associated with it.

 
Synchronization of Products and Services Data 
  
Vtiger to QuickBooks
Products/Services is a single entity in QuickBooks, whereas Vtiger offers Products and Services as two different modules. During the sync process, Products and Services in Vtiger are jointly mapped as the Products/Services module in QuickBooks.

QuickBooks to Vtiger

• Records in Products are synced to the Products module in Vtiger CRM.
• Records in Services are synced to the Services module in Vtiger CRM.

Synchronization of Vendor Data
 
Synchronization of Vendor Data