A smart lock is an electromechanical lock which is designed to perform locking and unlocking operations on a door when it receives such instructions from an authorized device using a wireless protocol and a cryptographic key to execute the authorization process.
It also monitors access and sends alerts for the different events it monitors and some other critical events related to the status of the device. Smart locks can be considered part of a smart home.
Most smart locks are installed on mechanical locks and they physically upgrade the ordinary lock. Recently, smart locking controllers have also appeared at the market.
It's like the traditional locks and key. In the case of these electronic locks, the key is not a physical key but a smartphone or a special key fob configured explicitly for this purpose which wirelessly performs the authentication needed to automatically unlock the door.