Body changes, also known as puberty, is when you grow up and your body starts to become like an adult’s body. If you are a girl you become curvy, grow hair in certain places, become fertile and get periods. If you are a boy you can get broader and also have hair grow in some places. You may find that you need to shower more and use deodorant.
It can be strange to experience your body changing, but it is totally normal and you can find lots of information about it online.