Cannabinoids are the Alkaloids in Marijuana, Ex: THC, THCA, CBD, CBN
are the "substance" in Marijuana that is making you "high". We aren't
really sure why Cannabis has Cannabinoids, but some people believe it is
to keep water off of it's buds, to prevent mold. I personally would
like to think that it knows what it is doing, and made THC in an attempt
to attract animals.
But all we can do is theorize as to what they are there for.
But that is what they are.
They are molecules with carbon bonds inside a plant, that react with our brains, to make us happy, or "high".