NFC Tag
A tiny, battery-free chip with an antenna coil that stores data - typically a URL - and wakes up only when a phone gets close.
An NFC tag is a thin sticker or insert containing a tiny memory chip and a copper coil that acts as an antenna. No battery needed - the tag harvests energy from the phone's electromagnetic field and sends back its stored data.
Data is stored in a standard format called NDEF, usually a single URL. You can embed a tag in a card, sticker, or table sign, and print a QR code on top as a fallback for devices without NFC.