Liver cirrhosis is the chronic strain and infection of the liver. The liver breaks down alcohol. When the liver is strained it can get infected. The infected cells die and are replaced by connective tissue. These are actually little scars. Because of the connective tissue, the liver functions less efficiently and can no longer recover.
Not everybody who drinks excessively gets liver cirrhosis, but anomalies in the liver often remain unknown or are discovered only after many years. Research conducted on deceased people who were known for drinking more than 5 alcoholic beverages a day showed that 20% suffered from liver cirrhosis.