Quick Answer: Print on demand is a printing technology and business process in which book copies are not printed until the company receives an order, allowing prints in single or small quantities. While other industries established the build-to-order business model, POD could only develop after the beginning of digital printing, as it was not economical to print single copies using traditional printing technologies such as letterpress and offset printing. Many traditional small presses have replaced their traditional printing equipment with POD equipment or contracted their printing to POD service providers. Many academic publishers, including university presses, use POD services to maintain large backlists; some use POD for all of their publications. Larger publishers may use POD in special circumstances, such as reprinting older, out-of-print titles or for test marketing.