Viagra is a widely recognized medication available in four strengths: 50 mg, 100 mg, 150 mg, and 200 mg. It contains sildenafil as its active ingredient and is primarily used to treat erectile dysfunction, commonly known as impotence, in men. This medication is produced by reputable manufacturers and is also marketed under various brand names including Revatio, Cenforce, Fildena, Aurogra, Malegra, Filagra, Sildigra, and LeeForce.