One of the main liver diseases is hepatitis—an inflammation of the liver caused primarily by viruses, but also by caused by autoimmune conditions, genetics and some poisons.
Hepatitis A is often in the news from bad food—for instance, a preparer who didn't wash his or her hands properly can poison food with the hepatitis A virus.
Hepatitis B and C can be spread through sexual contact, IV drug use and tattooing, with C being the virus more likely to transition to a chronic infection and cause cirrhosis, which is when scar tissue forms in the liver and replaces dead liver cells. Too much alcohol is a common cause of cirrhosis, but contact with other liver toxins can also kill off liver cells to cause cirrhosis.
Your liver is also susceptible to cancer, although cancer in the liver often occurs when it spreads there from a primary source in another organ, like the colon.