Radio-frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader.

Radio-frequency identification comprises interrogators (also known as readers), and tags (also known as labels).

Most RFID tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating a radio-frequency (RF) signal, and other specialized functions. The second is an antenna for receiving and transmitting the signal.

There are generally three types of RFID tags: active RFID tags, which contain a battery and can transmit signals autonomously, passive RFID tags, which have no battery and require an external source to provoke signal transmission, and battery assisted passive (BAP) which require an external source to wake up but have significant higher forward link capability providing great read range.

The EPCGlobal standard (uhfc1g2_1_1_0-standard-20071017.pdf from EPCGlobal) defines four classes of tags as class 1, class 2, class 3 and class 4. Each successive class has higher functionality than the previous one and is also backward compatible. Apart from these four classes, sometimes class 5 is also referred by users in the industry which are nothing but RFID readers.

RFID has many applications, for example, it is used in enterprise supply chain management to improve the efficiency of inventory tracking and management.