what is "ADD"

How are you Dr. Hallowell  I'm a Taiwan peopole (sorry my english is pool)

at time in bookstore I seen your book "Delivered from Distraction" , I found I like a "ADD"  and very interested it ,but in taiwan I can't

search some good for me to very understend about "ADD"  so I sreach about you by web ,I'm so sorry about my english is very bad  but

I really want to know what is ADD and learn how to be better.            very thankyou look my write letter   by Gary Jun in taipei