Here's how it was explained to me once:

1. There is external hyperactivity (like Ace Ventura or any other Jim Carey character)

2. There is internal hyperactivity (Racing thoughts, excessive talking, anxiety-like symptoms, etc.).

Those with ADHD all have hyperactivity, it just manifests differently across the subtypes (ADHD-Predominately Hyperactive, ADHD Predominately Inattentive, and ADHD-Combined).