A gross sale is the overall sale that isn’t adjusted for any kind of customer discounts or returns, or any other figure. It is thus the total invoice value of sales.
It is different from Net Sales which deducts the following
1. Sales Allowances : In case of defects
2. Sales Discounts : Discounts offered on mark up prices
3. Sales Returns : In case products are returned for refunds
Gross sales doesn't take into account the above 3 factors. Also it doesn't take into consideration all sources of income for a company whereas Revenue does that.