The Buy Box is the display on a Product detail page with the Add to Cart button that customers can use to add items to their shopping carts. When one of your listed items appears as the default on the product page, you “win” the Buy Box, increasing your chances of selling that item.
If you are a Fulfilment by Amazon (FBA) seller, your FBA new offers are automatically eligible to win the Buy Box. Otherwise, you must meet all of the conditions listed below. Amazon does not guarantee placement in the Buy Box.
You can find out if any of your items are eligible for the Buy Box:
The Buy Box Eligible column will display the status for each of your ASINs.