What is the difference between Net Sales, Net Payments, Gross Sales, and Gross Payments?

Net Sales are payments collected for product sales only, less returns

Net Payments are total payments collected and include product sales, gift card sales, shipping income and sales tax collected, less return payments. 

Gross sales are sales at full retail price.

Gross Payments are total payments collected and include product sales, gift card sales, shipping income and sales tax collected.