Radio frequency identification or RFID is a kind of technology that involves radio frequencies or signals for obtaining and sending the information. There are two kinds RFID tags which are active and passive tags. Active tags contain built-in battery system so they can directly transmit the information. This is why these tags are expensive.
Passive tags require external source of power for transiting the data. Research and development are in progress for making RFID technique more accessible and cheaper. You may search for the RFID chip timing Palmdale California on the Internet to get valuable information on this regard.