Why is CBD different from THC

Cannabidiol (CBD) is a compound extracted from the Hemp plant which is a derivative of Cannabis Sativa. Cannabis and Hemp plants are both derivatives of the Cannabis Sativa plant.
The concentration of CBD and THC in the Hemp and Cannabis plants constitutes the main difference as they’re higher in the respective plants and therefore depending on the intended use, manufacturers concentrate on one or the other.
Hemp plants do have tetrahydrocannabinol (THC) at low concentration levels but their concentration of CBD in their leaves and flowers makes them more attractive to manufacturers who derive the compound to make CBD products. The constitution of CBD is not dependent on which plant it is extracted from (Hemp or Cannabis) therefore its effects remain constant while the opposite cannot be said of Cannabis.
Another difference is starkly shown in the effects of consuming the compounds. Cannabis has known psychoactive effects as a result of the THC including; loss of memory and elevated heart rate while CBD has no known physical or mental side effects.
Legality
The other key difference comes down to the fact that the hemp plant that contains CBD was first legally separated from the marijuana nomenclature and also struck from the Controlled Substances Act. CBD products with under 0.3% THC are legal while above that percentage are still considered marijuana and therefore federally illegal. Different states therefore have different legality provisions for CBD products.
Consumption & usage
Another key difference is revealed via how these two compounds are consumed; Cannabis is smoked, mixed with edibles and there are various oils laced with THC available. CBD is consumed as a cheek aerosol spray, vaped, rubbed or as CBD oil with a high CBD concentration.
Cannabis has been used as a recreational drug and medicine for glaucoma and epilepsy among many other ailments while CBD has been used for pain relief and the treatment of other ailments are being explored.
CBD and Cannabis have many similarities but when broken down are fundamentally different compounds with different physical and effective manifestations.