RFID, or radio frequency identification, is a method where a reader powers and reads a tag over radio. Passive UHF RFID can reach several metres, and NFC is a special short range case of RFID.
The longer version
Radio frequency identification lets a reader detect and identify a tag using radio waves. In passive setups the reader's signal powers the tag, which reflects back its stored identifier. There is no battery in the tag, which makes RFID cheap enough to place on pallets, badges, and inventory.
Range depends on the frequency. Passive UHF RFID can reach several metres, which suits reading many tags across a warehouse or a doorway at once. NFC sits at the very short end of the same idea, tuned to a few centimetres so an exchange only happens on a deliberate, close tap.
RFID answers the question of what is present rather than how a payment should route. It can identify a tag near a reader, but on its own it does not resolve which of several parties is nearest, nor does it move money. Turning presence into a trustworthy transaction takes a way to settle the nearest pairing and route payment safely.
The Parousya method
RFID and NFC show the range trade the Parousya method navigates. The method senses presence over a short range signal, then routes the transaction through a central server, so identification and payment stay separate from the tag read itself.