Radio frequency identification (RFID) is a method of identification that uses tags stuck onto a product, in order to store data that can be retrieved by a reader.
RFID is often used to track pallets of products from the manufacturer to the retailer.

RFID is based on a transmission and reception of radio frequency (RF) signals between a transmitter (the reader) and a transponder (the tag)(which is attached to the product).

Active Transponders:
are battery powered and can be read over a great range, several tens of metres. They are typically expensive and are usually only used on vehicles and shipping containers. Battery powered; therefore it has a limited lifetime.

Passive transponder:
take the power they need to respond from the electromagnetic signals transmitted from the receiver. The strength of the signal falls quickly and has a limited read range. Commonly used for tracking pallets and library books.