A purchase order in retail serves as a formal request to a vendor to provide specific merchandise. It typically includes important details such as item descriptions, quantities, prices, and delivery instructions. This document is crucial for establishing clear communication between the retailer and the vendor, ensuring that both parties have a mutual understanding of what is being ordered and the terms surrounding that order.
In contrast, other options describe different aspects of retail operations. For instance, a list of items sold during a particular time pertains to sales tracking rather than ordering. An inventory management system refers to tools and processes used for managing stock in warehouses, not a document for ordering. A form to return unsold merchandise addresses the logistics of handling excess stock rather than initiating a new purchase. Thus, the true essence of a purchase order is encapsulated in its role as a request for merchandise, making the selected answer accurate.