Esophageal varices most commonly occur in patients who

Esophageal Varices (or how I sometimes describe esophageal hemorrhoid...) are blood vessels the protrude through the esophageal wall, as a result of increased pressure. These varices mostly originate when some problem results in the Portal and Hepatic arteries and vein (the vessels that supply the liver), such Portal hypertension (the increased blood pressure through the Portal Artery) or Hepatitis. These blood vessels if under a lot of pressure or are exposed to the acid of the stomach (in diseases such as GERD), they can rupture or tear causing hemorrhage and hence hematemesis (blood in vomit). This can be a life threat.   

Varices are very common in patients who have caused some sort of degeneration of the liver, usually through copious drinking.