A Google review card is a small, programmable card that sends a customer straight to your business's Google review page. Instead of asking someone to search for you, scroll past the wrong listing, and hunt for the review button, you hand them a card. They tap it with their phone — or scan the QR code printed on the back — and the review screen opens, already pointed at your listing.
The technology behind it is NFC: the same near-field chip that powers contactless payment. That's all a "tap card" is. No battery, no charging, no pairing. Just a chip that holds a link and hands it to any phone held within a couple of centimetres.