Diarrhea is loose, watery stools. Having diarrhea means passing loose stools three or more times a day. Acute diarrhea is a com­mon problem that usually lasts 1 or 2 days and goes away on its own.
Diarrhea lasting more than 2 days may be a sign of a more serious problem. Chronic diarrhea—diarrhea that lasts at least 4 weeks—may be a symptom of a chronic disease. Chronic diarrhea symptoms may be continual or they may come and go...

FOR MORE DETAILS http://digestive.niddk.nih.gov/ddiseases/pubs/diarrhea/