We understand that it can get confusing, but although hemp and marijuana are both classified as cannabis sativa in the plant world, hemp and marijuana are very different plants and CBD and THC are very different cannabinoids. Some of the confusion comes because genetically, hemp is always classified as cannabis sativa and many forms of marijuana can be classified as cannabis sativa as well (marijuana can also be cannabis indica or less often cannabis ruderalis). Since both hemp and marijuana plants can be cannabis sativa, it stands to reason that many people assume that they are identical. Wrong! Just as cucumis melo can be either a musk melon or a honeydew melon (very different melons), cannabis sativa can be hemp or marijuana (two very different plants).
The true, practical difference is how hemp has been bred compared to the marijuana form of cannabis sativa. Hemp is very fibrous, with long strong stalks and barely any flowering buds, while marijuana forms of cannabis sativa will be smaller, bushier and full of flowering buds. Marijuana, almost always, has a high amount of THC and only a very low amount of non-intoxicating cannabinoids such as CBD. Hemp, on the other hand, naturally has a very high amount of CBD and only a trace amount of THC. In other words, THC from marijuana will get you high; while CBD from hemp will get you healthy.