A freezer is an appliance that keeps food extremely cold, usually around 0°F (or -18°C), cold enough to freeze water solid. At this temperature, food stops spoiling because the bacteria and mold that make food go bad can't grow.

Most homes have a freezer as part of their refrigerator or as a separate chest in the garage or basement. Inside, you might find ice cream, frozen vegetables, meat for future dinners, or ice cube trays. Some families freeze leftovers or extra bread to keep them fresh for weeks or months instead of days.

Before freezers became common in the 1940s, people relied on iceboxes (which used large blocks of ice) or had to preserve food by canning, salting, or drying it. The invention of the home freezer transformed how families store and prepare food, making it possible to buy groceries less often and waste less food.

When you put a wet ice cube tray in the freezer, the water freezes into solid cubes. Similarly, anything with moisture in it can become rock-hard in the freezer, which is why freezer burn (those white, dry spots on frozen food) happens when food isn't wrapped tightly and moisture escapes.