ADHD stands for Attention-Deficit/Hyperactivity Disorder. Sometimes, people refer to ADHD as ADD, Attention Deficit Disorder. ADHD is a neurodevelopmental disorder that affects both children and adults. ADHD manifests differently in everyone but can affect their ability to pay attention, control impulses, and regulate their activity levels. ADHD is typically characterized by a persistent pattern of inattention, hyperactivity, and impulsivity that goes beyond typical behaviors for a person's age.