A merchant is either an individual or a company that sells goods or services. The merchant will sell products for a profit and facilitate customers during their buying journey. Merchants can operate as retailers or wholesalers, and any source could sell items to another source.
So before the Merchants work with Design, they meet with Buying to review the financial plan to ensure everyone is aligned. Once the Merchants present the product offering / collection, the Buyers are the ones purchasing it. Deciding how many units of each item will be bought, for how long, and for what stores.