Aphasia is the reason ExpressAgain exists: the person can think, read and understand, but the words will not come out. The app's core library, the Learn courses, Practice Out Loud and the family circle were built for it first, and the Aphasia and Stroke mode is the one that is fully built today. The public aphasia page explains the types (expressive, receptive, global, anomic) in plain words.
The condition page on the public site tells the full story and ends with the way to create an account.