Terpenes are organic compounds that provide the aroma and flavor in cannabis and a variety of other organisms, mostly plants. Terpenes are plentiful within the plant world. Terpenes are responsible for the citrus smell of a lemon, the fresh scent of a pine tree, the sensual aroma of patchouli, and the stimulating scent of eucalyptus.  In most cases, if a plant has an aroma or a flavor, it is because of a combination of different terpenes.

Although hundreds of different terpenes have been found in plants, there are a handful of terpenes that are naturally occurring in cannabis including limonene, caryophyllene, myrcene, humulene, and pinene. Besides being aromatic, many terpenes are bioactive, meaning they have physical and mental effects, from reducing inflammation to providing sedation. Mounting scientific evidence suggests that terpenes create synergy with other cannabinoids, increasing their therapeutic value. This is called the Entourage Effect, and it's the reason these aromatic compounds have become such a critical area of cannabis research.

Because terpenes are a critical part of the benefits we reap from products like CBD oil, it is important to choose a full-spectrum CBD product, rather than a broad-spectrum product or CBD isolate, so you can enjoy the full range of terpene-related benefits.

Source:

https://www.sciencedirect.com/science/article/abs/pii/S0009279717310487

https://www.medicalnewstoday.com/articles/what-are-terpenes#effects

https://www.leafly.com/news/cannabis-101/terpenes-the-flavors-of-cannabis-aromatherapy