A third-party (3P) seller uses the Amazon marketplace to sell directly to shoppers and handles customer service for all of their products. 3P sellers' items are displayed as “Sold by Merchant and Fulfilled by Amazon" or "Fulfilled by Merchant."
Amazon Seller Central is a marketplace interface that brands and third-party merchants use to manage all aspects of their Amazon business. Alternatively, Amazon Vendor Central is a platform that enables Amazon itself to sell products on behalf of brands.
Since the start of 2022, Amazon has been reducing its private-label offerings and discontinuing sold-out items. The most recent rumor? That Amazon may exit the private label scene altogether.