Cannabinoid receptors CB1 and CB2, located throughout the body, are part of the endocannabinoid system, which is involved in a variety of physiological processes including appetite, pain-sensation, mood, memory and more!
The main reason that cannabis provides psychoactive effects as well as therapeutic benefits is because the cannabinoids in the plant interact with the receptors, much like a lock and key.The receptor is the lock and the cannabinoid molecule is the key.