You know how sometimes your friends grow taller than you really quickly? It's because they're going through something called a growth spurt. But sometimes, some kids grow slower than others and that's what we call a constitutional growth delay.
It means that even though you might be shorter than your friends now, you will still grow and catch up to them eventually. It's like a race where some people start running earlier than others, but everyone will eventually finish at the same time.
It's not a bad thing, it just means that your body is taking its time to grow properly. You might have to wait a little longer than your friends to reach your full height, but it will happen. Some people who have constitutional growth delay might even end up taller than their friends in the end!