Most locks that involve entering a number are known as combination locks. The numbers are usually arranged in turn dials, twistable knobs, or dial pad entry format. These types of locks come with a preset number that has to be entered in sequence to open the lock.
A permutation can be thought of as a set of numbers in a sequenced order. Almost all combination locks should actually be known as permutation locks because the order of the numbers that must be entered cannot be switched.
A lock that has interchangeable numbers can be categorized as both combination and permutation. For example, if a lock has the combination "555" this can be thought of as a combination lock in that you could switch any 5 with any other 5 and still unlock the lock. It can also be thought of as permutation in that the fives are in a specific sequence of one following another.
The terms combination and permutation are often confused and switched because of their close meaning. The term permutation is thought of as a more exact mathematics term rather than combination, which is more of a general term. However, in terms of the lock industry, these two words are often used interchangeably.