An RFID Tag is an electronic circuit and one or more antennas that use RF waves to communicate an identifier which allows it be differentiated from other electronic circuits.
RFID tags are attached to, affixed to, or embedded in, inanimate or animate objects for the purpose of unique identification. Since the tag is what is identified, an association must be created between the tag and the object. The word "tag" is commonly used because the electronic circuit is typically designed for the purpose of being associated with something else. RFID tags are often used to determine the approximate location of the object to which it is associated.
RFID tags can be categorized by the method in which is it powered. The most common terms used for differentiation in this manner are:
- Passive RFID Tags
- Battery-Assisted Passive (BAP) RFID Tags or Semi-passive RFID tags
- Active RFID Tags
RFID tags communicate using different radio frequencies (see Common frequencies used by RFID technology).
The RFID Tag Communication Protocol defines the method of communication used by the RFID tag or more simply, how the tag talks.
The RFID tag data refers to the information stored by the RFID tag. At a minimum, there is some kind of identifier. If there is no identifier, then the electronic circuit is simply a device that uses RF and not related to RFID.
There are RFID Standards and Regulations which define, and govern, the power, communication, tag data, and other characteristics of RFID tags.
RFID tags are sometimes referred to as wireless sensors. This is most accurate when the RFID tag also has another type of sensor, such as temperature, shock, vibration, etc.