What is the Constant Contact integration with Vtiger CRM?

Vtiger CRM provides multidirectional data sync with Constant Contact. Integrating Constant Contact with Vtiger CRM syncs contacts available for the Contacts module with the Constant Contact portal and vice versa for every contact created, updated, and deleted. 
You can sync available contact records in the following ways:

• Sync from Vtiger to Constant Contact 
• Sync from Constant Contact to Vtiger 
• Sync both ways

Note: Constant Contact Integration is available only for the Contacts module in Vtiger CRM.