Some parts are there in RFID tags. These are integrated circuit to process and store the information to modulate and demodulate the signals that includes radio frequency. It is the way to obtain DC power from the reader. The tag has an antenna to get and send the signal.
The tag information is stored in a non-volatile memory. The RFID tag involves fixed or programmable logic for processing the program and sensor data, correspondingly. In order to get more information on RFID, you may search for RFID Chip Timing Nampa Idaho on the Internet.