So what’s the difference?
Traditionally, locks like those used in doors have a single key pattern or “cut”, which means everyone who needs access to that door will receive a identical copy of that specific door’s key. Once keys are distributed, it is impossible to know who is accessing that lock or if anyone has made copies. It is also very difficult to revoke access to one specific person, especially if you cannot recover the physical key from them, or it is lost. It also means that everyone will need a keychain with a different key for each lock they should have access to.
RFID systems work the opposite way. Instead of each door lock being unique and issuing copies of keys, each key is unique and door locks simply maintain an “authorized list” of each RFID unique serial number allowed through that door. This means each person only needs one RFID card to access any door they are authorized to access, and control over the authentication mechanisms are retained by the people in charge of securing the doors. Also, any RFID device can easily be revoked even if physical recovery of it is not possible.