A stool should be solid, but moist and easy to pass. Receives food and liquid we eat and drink. Absorbs most of the nutrients from food and drink into the blood-stream. Secretes fluid from the body into the gut. Excretes waste material as stool.
Diarrhoea means there are frequent, loose or liquid stools.
Acute diarrhoea - comes on suddenly and lasts a short time. Chronic diarrhoea - affects someone over a long period of time. Some people pass frequent, small solid stools with a sense of urgency. This is not true diarrhoea and occurs when the rectum is irritable as in the irritable bowel syndrome or inflamed as in colitis. This is how some laxatives work.