Diarrhea is a condition characterized by an increase in the frequency and looseness of bowel movements. It can be caused by various factors such as viral or bacterial infections, food poisoning, stress, certain medications, or underlying medical conditions like irritable bowel syndrome (IBS) or celiac disease. Diarrhea can lead to dehydration and electrolyte imbalances if not properly managed, so it's important for individuals experiencing diarrhoea to drink plenty of fluids and consult a healthcare professional if symptoms persist or worsen.