The Amazon Buy Box refers to the prominent purchasing interface on Amazon's product detail pages where customers can directly add items to their shopping carts. When multiple sellers offer the same product, Amazon determines which seller's offer appears in the Buy Box based on a variety of factors such as price, fulfillment method (e.g., Fulfilled by Amazon or FBA), seller performance metrics (e.g., feedback ratings, shipping time), and availability of the product.

Having the Buy Box is crucial for sellers because the majority of sales on Amazon come through this feature. Winning the Buy Box can significantly increase a seller's visibility and sales. However, it's essential to note that not all products have a Buy Box, and its availability depends on various factors determined by Amazon's algorithms.