Fatty liver, also known as steatosis, is a condition where fat builds up in the liver. It is common and reversible through lifestyle changes. Fatty liver may cause no symptoms and does not typically cause permanent damage. It is diagnosed through blood tests, ultrasound imaging showing white fatty areas of the liver, or liver biopsy. Risk factors include obesity, diabetes, excessive alcohol use, malnutrition, and certain medications. Treatment focuses on managing underlying conditions and making healthy lifestyle modifications to reduce fat in the liver. The two main types are alcoholic fatty liver disease caused by heavy drinking and non-alcoholic fatty liver disease which has other potential causes like obesity, genetics, or high cholesterol.