First of all let me tell you what is RFID. RFID is short for Radio Frequency Identification, which is basically a very small chip which is embeded into anything for digital identification system, by anything I mean anything, this anything even includes YOU 🙂 Yes! even the human beings.
RFIDs are like tags. There is no need for a scanner to be close to the tag to read the data, i.e. and RFID transponder can be read by the RF device from even meters away, or even behind the wall.