Third-party (3P) selling refers to a multi-vendor marketplace model where individuals or businesses can sell their products alongside those of the main retailer. This model gives sellers access to a large customer base and the marketplace gets a wider selection of products to offer its customers. It's a great way for small businesses and individual sellers to get their products in front of more people without having to go through the hassle of building their own website or storefront. For operators, it's an opportunity to expand their assortment without taking on the inventory risk.