Vomiting (throwing up) happens when very strong stomach contractions force a large part of the stomach contents back up the swallowing tube (esophagus) and out through the mouth or nose. It is usually caused by a minor illness.
Vomiting is not the same as regurgitation. Regurgitation is the effortless spitting up of a small amount of food or liquid. Food goes up the swallowing tube and into the mouth. Regurgitation is very common in babies. It is not harmful. Audio available.