RFID stands for “Radio Frequency IDentification”. It is a near-field communications standard that has been used for many years on Oyster cards used with the London Underground, and many other identification based systems. You hold a tag or card in close proximity to a reader, and the reader reads a unique ID number stored in that tag to open a door or perform some action for you.
There are many different types and standards of RFID, and the one used here is the Mifare standard. This is the standard that was adopted by London Underground for the Oyster card, and is also used on various contactless payment systems.
The development of the RFID standard lead on to the original idea of “The Internet of Things”. If “Things” all have a unique ID, you can track those things as they move, and computers can make their own decisions about the world, rather than relying on humans to tell them what is happening. Read the fascinating article in ref[8] to find out more about the British inventor Kevin Ashton who was instrumental in the development of RFID, and who is attributed with coining the phrase “The Internet of Things”.