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 an identical copy of that key. Once keys are distributed, it is impossible to know who is accessing that lock or if anyone has made copies. It is also difficult to revoke access to one specific person, especially if you cannot recover the physical key from them, or it is lost. This means everyone needs a keychain with different keys for each lock they should have access to.
RFID systems work the opposite way. Instead of issuing identical copies of keys for each door, each “key” is unique and locks maintain an “access list” of RFID serial numbers. 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 from any list, even if physical recovery of it is not possible.