I am seeking advice on the best way to locate a record that is in one table and not another.

I currently have two tables. Vendor_Products which contains all the products for a vendor and Active_Inventory which contains products that are available as of the last update.  I want to search the Vendor_Products table using a field (product_ID) from Active_Inventory and locate data that doesn't exist in the  exists in the Vendor_Products but doesn't exist in the Active_Inventory  table.  Once I find a not found condition in the Vendor_Products table I want to output data to the Active_Inventory.