When we speak of normally open and normally closed, we can think of referring to the door, but in electric locks we refer to the state of the circuit.
NOT (normally open) means that 99% of the time the circuit is open, it is not powered and only 1% of the time it is powered to open the lock; this philosophy typically applies to Fail Secure systems.
Fail Secure: If there is no power, the lock will remain closed
However, when we talk about NC (normally closed) this means that 99% of the time the circuit is closed, the lock will be powered. And in the 1% it will stop being fed to open the lock.
This system is designed so that in the event of a power failure or emergency you can get out; this philosophy typically applies to Fail Safe systems.
Fail Safe: If there is no power, the lock will remain open.