Chills are when your body feels really cold and shivery, even if you're wearing warm clothes. When you have chills, your body is trying to warm up by shaking and shivering, like a little earthquake inside you!
Your body does this because it's trying to fight off an infection, like when you have a cold. Sometimes you'll get chills when you have a fever, which is when your body gets hotter than usual to fight off the sickness.
When you have chills, your body might also make your hair stand up on end, like you're a porcupine! This can make you feel even colder, but it's your body's way of trying to trap more heat close to your skin.
To help yourself feel better when you have chills, you can cuddle up in a warm blanket or sweater, sip on some hot soup or tea, and rest as much as possible. Your body will work hard to fight off the sickness and make you feel better soon!