ADHD stands for attention deficit hyperactivity disorder. ADHD used to be known as attention deficit disorder (ADD). ADHD is a disease that affects the concentration and focus of a person. The reason behind this disease is a difference in the parts of brain that control attention and activity. People having this disease may have trouble focusing on several things or they may seem wired to them.
ADHD has many different conditions and they vary from person to person, sometimes it shows up in early ages and sometime later at some stage, so a person suffering from ADHD might have these symptoms.