Hi,

Product margin is the profit that a company makes from sales of a product that you have either manufactured at your company or purchased from another vendor. An effective product margin analysis will help the company to get accurate information on the sales of the product.

The report displays the Name of the product, Internal Reference, Average Sale Unit Price (Average price in customer invoices), Invoiced in Sale (Sum of quantity in customer invoices), Turnover (Sum of multiplication of invoice price and quantity of customer invoices), Sale Gap (Expected sale- turnover), Total Cost (Sum of multiplication of invoice price and quantity of vendor bills), Purchased (Sum of quantity in vendor bills), Total Margin (Turnover- standard price), Expected Margin, Total Margin Rate, and Expected Margin Rate.

For more details, please refer the blog 
https://www.cybrosys.com/blog/an-overview-of-invoice-and-margin-analysis-with-odoo-16-accounting#:~:text=By%20considering%20the%20necessity%20of,tab%20of%20the%20Reporting%20menu.

Hope it helps