or Radio-frequency identification uses electromagnetic fields to automatically identify and track tags attached to objects.

An RFID system consists of a tiny radio transponder called a tag or load, a radio receiver, and a transmitter. When triggered by an electromagnetic interrogation pulse from a nearby RFID reader device, the tag transmits digital data, usually an identifying inventory number, back to the reader. This number can be used to track inventory goods, like chips.

There are two types of tags/loads: passive and active. Passive tags use the energy of the transmitted signal to re-transmit the signal (then encoded with the tag's number), which is detected by a receiver. The RFID tag has three components: an antenna, a microchip, and a substrate that connects the two.

No batteries involved for passive RFID.