Vomiting is the act of forcefully expelling the contents of one's stomach through the mouth. It is a common response to nausea and can be caused by various factors such as illness, food poisoning, motion sickness or stress. Vomiting helps to rid the body of unwanted substances and can be a natural way for the body to heal itself. However, excessive vomiting can lead to dehydration and other health problems, so it is important to address the underlying cause if possible.