What is data mapping in Salesforce?

Adobe Sign form field data mappings let you define how Adobe Sign will update Salesforce.com objects with data it captures from signers. For example, you can update a signer’s contact record in Salesforce.com with the address and phone number they provided when completing and signing your document. Additionally, you can also push back the Adobe Sign signed agreement, audit trail, and any uploaded supporting documents from recipients into Salesforce objects by setting up file mappings.
About Form Field Data Mappings
Adobe Sign Data Mappings update Salesforce objects when an Adobe Sign agreement is signed or at a specified stage in the agreement workflow. Each Data Mapping is set up ahead of time and includes data mapping rules. Each data mapping rule defines the data source and the target Salesforce field it needs to update.
A data source for a mapping can be an Adobe Sign form field, a specific constant value or a value from an Adobe Sign Agreement Field. The target for each data mapping item may be any field in any Salesforce object that can be referenced from the Adobe Sign Agreement.
For example, the mapping below updates the signer’s first and last name (as entered by the signer) in the Contact object. It also updates the Opportunity Stage and adds the signed agreement and audit trail to the Opportunity when the agreement is signed.