Cannabinoids are a group of chemicals that interact with the endocannabinoid system.
Marijuana is a source of over 60 cannabinoids, including THC and CBD. But the human body produces a number of cannabinoids as well. Cannabinoids found naturally in the body are called endocannabinoids. ‘Endo’ stands for endogenous, meaning within the body.
Common endocannabinoids include anandamide and 2-AG. These molecules are synthesized and released on demand. Their effects are shorter-lasting than marijuana because they are broken down faster by the body.
Guillermo V, Cristina S & Manuel G (2012), Towards the use of cannabinoids as antitumour agents. Nature Reviews Cancer, 12:436-444. doi:10.1038/nrc3247