Cannabinoids are the chemical compounds that really make Cannabis unique. There are a huge range of cannabinoids with each having a different effect on each different individual. Many cannabinoids produce entirely novel effects through the Entourage Effect, where the presence of multiple different cannabinoids and terpenes in different proportions results in completely unique highs! The most common cannabinoids are THC and CBD.
Cannabinoids interact with our body through our Endocannabinoid System. The Endocannabinoid System is naturally used for maintaining homeostasis, or a constant body temperature, and some cannabinoids are produced naturally within our own body. When cannabis is consumed, Cannabinoids from the cannabis bind to receptors in your body and cause the effects associated with cannabis.
The Endocannabinoid System is also found in every animal, both vertebrates and invertebrates, with the exception of insects, making the Endocannabinoid System very old in evolutionary terms.