What freezer burn actually is
Freezer burn happens when air reaches the food’s surface and ice sublimates — evaporates without melting — leaving dehydrated, oxidized patches. USDA is explicit: freezer-burned food is safe to eat if it has been continuously frozen at 0 °F. It is a quality defect: dry, papery texture and off flavors in the affected areas.
What it is not evidence of
Freezer burn does not indicate thawing, temperature abuse, or age-related hazard — and its absence doesn’t prove good history either. If you suspect the food thawed at some point (a failed freezer, a long outage, packages frozen into a block of former melt-water), that is a separate safety question the outage tool handles; freezer burn tells you nothing about it either way.
Using freezer-burned food
Trim heavily affected areas before or after cooking, and route the rest into wet, seasoned dishes — soups, stews, curries, braises — where the dryness disappears. Severely burned food is safe but may simply not be worth eating; that is a quality judgment you are free to make.
Prevention is packaging
Air is the culprit, so the fixes are airtight: press air out of freezer bags, use freezer-weight materials, wrap tightly, fill containers to the right headspace, and keep the freezer at a steady 0 °F. See packaging materials and air removal.