Tamiflu is an antiviral medication used to treat and prevent influenza, commonly known as the flu. It works by inhibiting the virus's ability to multiply in the body, helping to reduce the severity and duration of flu symptoms when taken early in the illness. This medication is most effective when started within 48 hours of the onset of symptoms. Tamiflu is available in capsule and liquid form and is typically prescribed for adults and children over the age of two. It is important to note that Tamiflu does not cure the flu but can help manage its effects.