What Does Rekeying a Lock Actually Mean?
Rekeying is often confused with replacing a lock. It is a narrower, more specific piece of work.
Rekeying changes the internal configuration of a lock so that a different key operates it. The lock stays on the door. Inside the cylinder, the components that must align for the lock to turn are changed so they correspond to a new key, and the previous key no longer works.
It is useful when the hardware is in good condition but the key situation has changed — keys that are unaccounted for, a change of tenancy, a change in who should have access, or a set of keys that has been distributed more widely than intended.
Rekeying is not the same as replacement. Replacement changes the physical hardware; rekeying changes only which key operates it. Because of that, rekeying is generally the lighter-touch option where it is available.
The important qualifier is availability. Not every lock is designed to be rekeyed, and a lock that is already worn or damaged is usually a candidate for repair or replacement instead. The specific hardware on your door determines whether rekeying is an option, so it is worth asking about your lock rather than assuming either way.