A cannabinoid is one of a class of diverse chemical compounds that acts on cannabinoid receptors in cells that alter neurotransmitter release in the brain. Ligands for these receptor proteins include the endocannabinoids (produced naturally in the body by animals),[1] the phytocannabinoids (found in cannabis and some other plants), and synthetic cannabinoids (manufactured artificially). 

a substance that is structurally or functionally similar to cannabinoids derived from hemp or cannabis:

a: any of several substances (as anandamide) naturally produced within the body.

The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis. The 2nd is Cannabidiol (CBD), which is another major constituent of the plant and is the main ingredient in Tru Medicinals products.

There are at least 113 different cannabinoids isolated from cannabis, exhibiting varied effects.