Electronic keyless locks may use a battery or they can be hard wired. Low power requirements make battery operated locks a cost effective choice for all but very high usage applications.
Programming can be accomplished in many ways, even directly from the keypad. You can get the same features Batteries last for a very long time and cost of installation is comparable to a standard lockset. for traffic control to a full blown access control system. Battery operated units draw very little power so batteries last a very long time depending upon usage.
Mechanical Keyless locks all use numeric keypads. Changing the code is a bit time consuming and best left to professional. Typically these are used for traffic control, not as your main locking device and in applications where combinations do not have to be changed often. They are single purpose and no bells or whistles.