Normally stomach is situated inside the abdomen while the oesophagus is inside the thorax (chest cavity ). In some cases upper part of stomach is pushed into the thorax, the condition is called Hiatal/ Hiatus Hernia, which has symptoms same as GERD. There are two main types of hiatal hernias: sliding hernia ( The stomach and the section of the esophagus that joins the stomach slide up into the chest through the hiatus).and paraesophageal (The esophagus and stomach stay in their normal locations, but part of the ,stomach squeezes through the hiatus, landing it next to the esophagus).