Viagra is a medication commonly used to treat erectile dysfunction in men. It works by increasing blood flow to the penis, helping to achieve and maintain an erection when sexually aroused. The active ingredient in Viagra is sildenafil, which relaxes the blood vessels and enhances the body's natural response to sexual stimulation. Viagra is typically taken as a pill about 30 minutes to an hour before sexual activity. It is important to note that Viagra does not cause an erection on its own; sexual arousal is still necessary. As with any medication, it’s essential to consult a healthcare professional before use to ensure it is safe and appropriate for individual health conditions.