A vendor is someone that registers on your marketplace to sell products. They maintain and manage their own products and can confirm shipping of orders. In pro they also have the ability to manage coupons, their complete store branding, shipping, ratings and more.
Jamie is the founder and lead developer of WC Vendors. He has been working in the WordPress, WooCommerce and Marketplace space for more than 15 years, 9 of those dedicated to multivendor marketplaces.