Diazepam, commonly known by its brand name Valium, is a long-acting benzodiazepine used to treat a variety of conditions, including anxiety disorders, muscle spasms, seizures, alcohol withdrawal symptoms, and as a sedative before certain medical procedures. It works by enhancing the effects of gamma-aminobutyric acid (GABA), a neurotransmitter that inhibits activity in the brain, thereby producing a calming effect.