Point-of-service (or -sale) (POS) hardware and the software that powers it are transforming customer experiences, sales associate experiences, store operations, and in-person sales. This report lays out key principles for POS and outlines how in-store payments work. It also gives payment executives at retailers and other consumer-facing businesses with physical locations the information they need to understand POS payments technologies, including fixed POS, mobile POS, and deviceless POS.