Radio-frequency identification (RFID) uses radio waves to automatically identify and track tags attached to objects.
An RFID system generally includes a tag, an antenna, and a reader. The reader sends an electromagnetic signal; a passive tag can draw energy from that signal and transmit stored data, often an identification number, back to the reader. Active tags contain their own battery and can communicate over longer distances or support additional sensing functions.
RFID became especially useful in supply chains because many tagged items can be identified without direct line-of-sight. A warehouse reader can scan cases or pallets as they pass through a portal, unlike a conventional barcode that normally must be visible and individually aimed at a scanner. RFID tags may also hold more data than a simple printed barcode.
NFC is a short-range technology related to radio-frequency communication and is commonly used for contactless payments. GPS determines location using satellite signals, while RFID identifies nearby tags; neither GPS nor a barcode is the canonical answer here.