Cannabidiol, or CBD for short, is a phyto-cannabinoid found in cannabis plants. However, it does not cause the same psychoactive effects as other naturally occurring cannabinoids (such as tetrahydrocannabinol, or THC). CBD induces feelings of sleepiness and tranquility, making it suitable for insomnia and other sleep disorders; CBD can be used to alleviate symptoms of epilepsy, diabetes, and anxiety disorders, as well. Legality is an issue for some; all 50 states have laws governing the sale, possession, and use of CBD, and they vary significantly (see the table below for a full analysis).
Currently, the only CBD product approved by the Food and Drug Administration is a prescription oil called Epidiolex. It's approved to treat two types of epilepsy. Aside from Epidiolex, state laws on the use of CBD vary. While CBD is being studied as a treatment for a wide range of conditions, including Parkinson's disease, schizophrenia, diabetes, multiple sclerosis and anxiety, research supporting the drug's benefits is still limited.