Acute gastritis refers to sudden inflammation of the mucosal lining of the stomach.  This inflammation weakens the mucosal lining, causing the stomach acid

Heartburn refers to irritation of the oesophagus from the acid in the stomach. Though it is called heartburn, this condition does not have anything to do with heart. 

Food Poisoning refers to illness that results from eating contaminated or spoilt food. It is a common occurrence as almost everyone will have food poisoning at