There are times when you want to fix or change a lock on one or many doors of your house. You do not always have to change out the entire lock hardware. Sometimes, you just need to re-key the lock.
When your locksmith re-keys the lock, he will make new keys for that lock, and reset the lock mechanism to work with that key instead of any other key. This is what should be done when you purchase a new home, just for security sake, because you never know how many keys are out there in the world for those door locks. For peace of mind, have the locks re-keyed.
Another situation arises when you have an existing lock, but are not allowed to change the lock mechanism. You may have lost a key, or have worn out keys that you need replaced. Your locksmith will create new keys for you that will operate that same locking mechanism. This is how you can get extra keys made also.
Replacing the entire lock is necessary when a lock is damaged or when its condition is weak or poor. You will receive extra keys along with your new lock hardware. A new lock is a security feature. Purchase a better style lock to upgrade your security. If replacing more than one door lock, you may want the locksmith to key them so that they all work with the same key. That way you only have to deal with one key for all.