Here is some information from KidsHealth, regarding ADHD.

What Is ADHD?

At times, all kids have trouble paying attention, listening, sitting still, or waiting their turn. But kids with ADHD have trouble with these things almost all the time.

Kids with ADHD aren't being this way on purpose. ADHD is a medical condition that affects their attention and self-control. Because of ADHD, they have a harder time staying focused. ADHD can also make kids more fidgety than other kids their age.

Kids with ADHD might have a tough time controlling their behavior and get into trouble more. This can make it hard to do things like pay attention in class or get along with others.

ADHD stands for attention deficit hyperactivity disorder. That's the medical term for difficulties with attention and self-control that can make kids fidget and move a lot.