This is inflammation of the liver, commonly caused by viruses.  Hepatitis B and C are viruses that can cause chronic (long term) inflammation and damage to the liver. These viruses are passed from person to person through body fluids.  For more information about Hepatitis B and C and their treatment see https://www.hepatitisfoundation.org.nz/ 

Alcohol can affect the liver and cause inflammation which, in the long term, can damage the liver permanently.

Excess weight, cholesterol and diabetes can also cause fatty liver which may in some cases cause hepatitis or inflammation in the liver.