From the YDL Forums
"Q: What's the definition of Net and Gross?
A:Net Revenue: In accounting, net profit is equal to the gross profit minus overheads minus interest payable plus/minus one off items for a given time.
Gross Revenue: gross sales: income (at invoice values) received for goods and services over some given period of time.
Put in simpler terms,
Net Revenue: Revenue you receive before any operational costs, merchandising costs, accounting fees and other services that may be listed in a contract.
Gross Revenue: Revenue you actually receive in your PayPal account, after any fees or costs taken out."