Marijuana and hemp are two different varieties of cannabis that come from the same species of plant (Cannabis sativa L). In general, CBD is found abundantly in both.
However it’s important to note that CBD is typically found in the seeds and stem of marijuana – not in the flowering buds (which is the part that you smoke). The hemp plant is an entirely different strain of cannabis that contains high quantities of CBD throughout (stem, buds, etc), and practically zero traces of THC. If a hemp plant contains more than 0.3% THC, it is then technically a “marijuana” plant. Most all CBD-based products come from the industrial hemp plant.