Cannabinoids are chemicals found in cannabis. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol, the primary psychoactive compound in cannabis. Cannabidiol is another major constituent of the plant. There are at least 144 different cannabinoids isolated from cannabis, exhibiting varied effects. (Wikipedia)
The most well known among these compounds is the delta-9-tetrahydrocannabinol (Δ9-THC), which is the main psychoactive ingredient in cannabis.