Hepatitis C is a disease of the liver that is caused by the hepatitis C virus. There are 6 different types (genotypes) of the virus. Some people who are infected with the hepatitis C virus get rid of it quickly without treatment but most people develop a long‑lasting infection; this is called chronic hepatitis C. People who have chronic hepatitis C may feel well for many years, but the virus causes damage to their liver later and can make them feel ill.
Ledipasvir–sofosbuvir (Harvoni) is a combination of 2 drugs in a single tablet and is used to treat genotypes 1 and 4 of the hepatitis C virus. It can get rid of the virus in some people who have never had treatment or who had treatment before that didn't get rid of the virus.
NHS Choices may be a good place to find out more.