The marijuana plant contains more than 60 different cannabinoids; chemical compounds the human body is uniquely equipped to respond to. The two primary ones are cannabidiol (CBD) and tetrahydrocannabinol (THC), the latter of which is the psychoactive component.
Cannabinoids interact with your body by way of naturally occurring cannabinoid receptors embedded in cell membranes throughout your body. There are cannabinoid receptors in your brain, lungs, liver, kidneys, immune system and more.
The therapeutic (and psychoactive) properties of marijuana occur when a cannabinoid activates a cannabinoid receptor. Your body also has naturally occurring endocannabinoids similar to THC that stimulate your cannabinoid receptors and produce a variety of important physiologic processes.