Key Lockable - handles and locks that require a key to gain entry. Most commonly used for external doors, they can be used for internal doors as well. Generally this furniture will be labelled as "entrance sets" or "storeroom sets" (different locking functions).
Lockable - handles and locks that are lockable, but are not unlocked by key. Most commonly these will be used on bathroom or toilet doors and usually described as "privacy sets".
Non-Lockable - these handles have no locking function at all and are generally used on internal doors requiring no security. This common label for this furniture is "passage sets".