Caryophyllene is a type of aromatic compound called a terpene. It can be found in many plants (rosemary and basil, for example), including the cannabis plant. Studies in mice have shown that it can affect the body’s endocannabinoid system to produce an anti-inflammatory response.
Experts such as neuroscientist Ethan Russo have speculated that terpenes like caryophyllene work in concert with THC and CBD to produce beneficial responses in the body. This phenomenon has been dubbed the Entourage Effect and you can read more about it here: https://www.hellomd.com/health-wellness/56d0f3acbbf86b000b0000ae/what-is-the-entourage-effect