Near-field communication - NFC - is the technology behind the "tap" in tap-to-pay. Two devices within a few centimetres exchange a short, encrypted burst of data, and the sale is done.
Why it caught on
It's fast, it's contactless, and it's secure - each tap generates a one-time token rather than exposing the real card number. For customers it's frictionless; for merchants it means faster lines and fewer abandoned checkouts.
What you need
Any modern terminal or NFC-enabled phone can accept it. If your hardware is more than a few years old, upgrading is usually the single easiest way to modernize the checkout experience.