How it works
The terminal creates a weak electromagnetic field, and the chip in the card or phone answers. The card needs no battery; it gets its power from the terminal's field.
Why a phone is safer than a card
The phone does not send the real card number but a one-time token. You have to confirm the payment with your face, fingerprint or a code. A stolen phone cannot pay without being unlocked.
Other uses
NFC is also used for pairing headphones, electronic keys, attendance cards (see Access control systems) and reading the chip in an identity card.