Motor neurone disease is a collective name for a group of progressive neurological disorders that destroy motor neurones. Amyotrophic Lateral Sclerosis (ALS) (sometimes called Lou Gehrig's disease), is one of the forms of MND as well as many others
Another excellent answer by Nigella. As a matter of interest, it matters not, are you medically qualified or a nurse or someone associated with medicine. Your answers are spot on.