RFID tag is a small device which stores and sends data to RFID reader. They are categorized in two types – active tag and passive tag. Active tags are those which contain an internal battery and do not require power from the reader. Typically active tags have a longer distance range than passive tags. Passive tags are smaller and lighter in size than the active tags. They do not contain an internal battery and thus depend on RFID reader for operating power and certainly have a low range limited up to few meters.
A rectangular passive RFID tag is shown in the above image. The passive tags are available in different shapes and sizes.
Removing the backside layer of the tag discloses the above look. A copper coil also known as the antenna is shown in the image above.