Vendor: This is an outside entity that you use to print jobs that your customers have ordered from you. The order comes to you from either a retail site or a customer storefront that you have set up in the system. You see that order in your admin area, choose "Edit Item," and choose the vendor to send the order to.
Broker: In this situation, you have a broker that orders from you on behalf of THEIR customer(s). You can either set up a customer storefront for your broker to access and order directly from you, or you can set up a customer storefront for the broker's customer(s). You then brand that specific customer's store to use the broker's logo (instead of your logo), along with the customer's logo. This storefront would have the products you print for this customer; they would login and order products from you. Your broker would be notified of the order that you received.
Note: You are the one who owns the subscription, the only one who receives orders and payments and the only one who accesses the administrative side of the system. You are able to build multiple storefronts (depending on your plan). We encourage you to set up as many of your repeat customers in those storefronts so they can order directly from you in their own branded site. The broker interface is beneficial because it allows you to extend that same benefit to your broker's customers.