Benzodiazepine is a class of therapeutic agents capable of producing a calming, sedative effect and used in the treatment of fear, anxiety, tension, agitation, and related states of mental disturbance.  Benzodiazepines are generally used only on a short-term basis to treat anxiety disorders, insomnia, and muscle spasms. Because they can be habit-forming, these medications aren't a good choice if you've had problems with alcohol or drug abuse.
The Encyclopedia Britannica1explains that benzodiazepines ease anxiety by impacting chemical messengers - neurotransmitters - used to communicate between brain cells. Benzodiazepines work by enhancing the action of the neurotransmitter gamma-aminobutyric acid (GABA), which inhibits anxiety by reducing certain nerve-impulse transmissions within the brain. These drugs act as sedatives by slowing down the central nervous system.
Examples include (brand name italicized):
- Alprazolam (Xanax)
- Chlordiazepoxide (Librium, Librax)
- Clobazam (Onfi)
- Clonazepam (Klonopin)
- Clorazepate (Tranxene)
- Diazepam (Diastat, Valium)
- Lorazepam (Ativan)
- Quazepam Doral
- Temazepam (Restoril)
- Triazolam (Halcion)
- Exaggerated response to alcohol
- Slowed down thoughts and psychical movement
- Memory problems while on the drug
- Loss of appetite
- Physical dependency on the drug
- Difficulty breathing while on opiates
- Paradoxical disinhibition (acute excitability)
 The Editors of Encyclopedia Britannica. “Benzodiazepine.” Encyclopedia Britannica, Encyclopedia Britannica, 5 July 2017, www.britannica.com/science/benzodiazepine.
 Longo, Lance P, and Brian Johnson. “Addiction: Part I. Benzodiazepines--Side Effects, Abuse Risk and Alternatives.” American Family Physician, vol. 61, no. 7, Apr. 2000, pp. 2121–2128.