Frostbite is what happens when your body gets so cold that your skin and other parts start to freeze. It's like when you put water in the freezer, and it turns into ice.
When it gets cold outside, your body tries to keep all your toes, fingers, nose, and ears warm by sending extra blood there. But if you stay in the cold for too long, your body can't keep up, and the extra blood can't stay warm enough. This is when frostbite can happen.
When parts of your body start to freeze, they can start to turn colors like pale or even blue. If they start to hurt or tingle, that's a warning sign that you need to get inside and warm up right away.
The best way to prevent frostbite is to dress warmly with hats, gloves, and thick socks. If you start to feel too cold, you should tell a grown-up and get inside where it's warm.