What it actually is
Freezing produces crystals whose size depends on how fast it happened. Storage then does something separate: every temperature fluctuation melts the smallest crystals a little and refreezes that water onto the larger ones. Over weeks the population shifts from many small crystals to few large ones, without the product ever thawing.
Why it matters
In ice cream it is the difference between smooth and sandy, and it is the most common reason a product is rejected after months in a cabinet that never technically failed. In frozen food it is what tears cell structure and produces drip on thawing.
What changes it
Freezing rate at the start, and after that the stability of the storage temperature rather than its absolute value. A cabinet held steadily at a slightly higher temperature damages a product less than one that cycles around a lower one. Stabilisers slow the migration of water between crystals.
