Hemp: The "non-drug" variety of the cannabis plant has been used for thousands of years. It has been known to have health benefits but only recently have scientists discovered that hemp contains a cannabinoid called CBD.
CBD: This non-psychoactive cannabinoid is one of more than 60 compounds also found in hemp. CBD acts on the body's endocannabinoid (internal cannabis) system, creating noticeable changes in the body, which can be beneficial in many ways.
Long story short - hemp is the plant and CBD is a compound within the plant.