Re-keying a lock involves changing the internal pins and tumblers of an existing lock cylinder so that it will only work with a new key. Essentially, the lock is taken apart, and the internal mechanism is reconfigured so that a new key can be used to operate the lock. This is often done for security reasons, such as when you move into a new home or business and want to ensure that previous occupants or employees cannot gain access with their old keys. Re-keying a lock is typically less expensive than changing the entire lock and can be done quickly and easily by a locksmith.
Changing a lock involves removing the entire lock and replacing it with a new one. This can be necessary if the lock is damaged, worn out, or if you want to upgrade the security of your property. When you change a lock, you are essentially replacing the entire locking mechanism, including the cylinder, latch, and strike plate, with a new one. This can be more expensive than re-keying a lock, but it can provide a higher level of security and can be a good option if you need to upgrade the lock on your door or if you want to switch to a different type of lock altogether.
In summary, re-keying a lock changes the internal pins and tumblers of an existing lock so that it will work with a new key, while changing a lock involves removing the entire lock and replacing it with a new one. Both processes can be useful depending on your specific needs and goals.