Xanax, or alprazolam, is a benzodiazepine used to treat anxiety and panic disorders by slowing down brain chemicals. It is available in dosages of 0.25 mg and 0.5 mg, but should not be taken by pregnant women or individuals with certain medical conditions, and can lead to addiction. Side effects include drowsiness and serious issues like mood changes, and it is advised to purchase Xanax through authorized medical channels to ensure safety.