Happens when part of your stomach bulges up through the diaphragm and into your chest. The diaphragm is a sheet of muscle that separates your belly (abdomen) from your chest.
The hernia bulges through the diaphragm at a place called the hiatus. This is the opening in the diaphragm that the esophagus passes through. The esophagus is the muscular tube that connects the throat to the stomach.
There are three main types of hiatal hernia: sliding, paraesophageal, and mixed. Most people who have a hiatal hernia have a sliding hiatal hernia.