Acid and bile coming from the stomach into the oesophagus may cause heartburn.

The normal oesophagus (gullet or food pipe) is lined with a pinkish-white tissue called squamous epithelium (left image).

Barrett's oesophagus is a condition in which the normal squamous epithelium of the oesophagus has been replaced by an abnormal red columnar epithelium (right image).

In the US it is referred to as esophageal cancer / cancer of the esophagus.