Teeth are the things in your mouth that let you chew food. They are hard and whitish and come in different shapes and sizes. We have two sets of teeth in our life, baby teeth and adult teeth. Baby teeth come in when you are a baby and then when you are about 6 or 7 years old, your adult teeth start to come in and push out the baby teeth. People brush their teeth every day to make sure they stay healthy and strong.