I have a genuine question for this community/subreddit with regards to food preservation methods/techniques that were used during the Middle Ages.

I know that the concept of "refrigeration technology" didn't appear until long after the Middle Ages had ended, but I keep hearing and/or reading online about the existence of "ice houses"; buildings that were specifically for storing food at lower temperatures and/or freezing them.

So I need some clarification regarding this matter. Did people during the Middle Ages/Medieval Period have some understanding of the idea that storing food at lower temperatures and/or freezing them was a good way to preserve the food's freshness? And if so, what methods/techniques do we have official records of them using to achieve this goal?