What is functional memory in humans?

All memory is in a sense 'functional' and is generally categorized into those that are 'implicit' (i.e., do not require conscious recollection, like knowing how to ski) and those that are 'explicit' (i.e., that involve conscious recollection of facts and experiences, like knowing where the best place to ski is). Psychologists make further distinctions within these two broad groups; but the point I wanted to make is that for a memory trace to work it has to be functional.