An RFID transponder is known as a tag and it includes a microchip for storing little amount of information. An antenna is attached for sending the signal through the short waves over a small distance to the reader. An active tag includes a battery and is used to send the signal but it is more costly.
On the contrary, passive tags do not include a battery and these are not expensive. Passive tags are required to be activated by the reader for accessing the data kept on them. You may look for the RFID chip timing Mobile Alabama on the Internet for more information.