ADHD (Attention-Deficit/Hyperactivity Disorder) is a neurodevelopmental disorder that affects both children and adults. It is characterized by persistent patterns of inattention, hyperactivity, and impulsivity that can interfere with daily functioning and development. Symptoms of ADHD often include difficulty focusing, forgetfulness, trouble following through on tasks, restlessness, and impulsive behavior. There are three main types of ADHD:

1. Inattentive Type (formerly known as ADD): Characterized primarily by problems with attention and focus, such as difficulty paying attention to details, being easily distracted, or forgetting tasks.
2. Hyperactive-Impulsive Type: Characterized by excessive fidgeting, inability to stay still, impulsive actions, and talking excessively.
3. Combined Type: This is the most common form and includes symptoms of both inattentiveness and hyperactivity/impulsivity.

ADHD is often managed through a combination of behavioral therapy, lifestyle changes, and medication, depending on the severity and individual needs.