If you're in your early teens or younger, your body isn't fully grown and alcohol will affect you more quickly than an adult.
It acts quickly, slowing your body down. In small amounts this can make you feel more relaxed but in large amounts it can be dangerous.
You may not be able to walk properly or speak clearly, but often you don't realise this.
You might feel sick, take stupid risks or lose control. If you're drunk you're a danger to yourself and to others.