Factually there is a measure of deficit to the ability for people with this issue, to maintain the focus of their attention on any particular thing, in a normal fashion. Normal being that neurotypical people can choose what they focus their attention on, and don't really have any trouble doing that.

The hyperactivity part, I believe is more about the physiological effects in the brain for people with the disorder. I'm not a doctor, but I believe one of the main characteristics of ADHD, is that dopamine receptors are hyperactive, leading to a deficiency of dopamine (and/or other signaling chemicals) in the brain. This can cause depression, anxiety... The list goes on.

So yeah. ADHD.

I dunno for sure. I'm just some guy with ADHD.