Amnestic disorders are conditions characterized by either the loss of memories or the inability to create new memories or learn new information. They are typically caused by brain disease, brain trauma, stroke damage, brain tumors, or substance abuse.
Amnesias are amnestic disorders.
Retrograde amnesia is a condition in which the sufferer cannot remember events before the amnestic disorder began. Anterograde amnesia sufferers can remember events from their past but cannot retain new knowledge or information after the onset of the amnestic disorder.