CBD is found in both hemp and marijuana. However, hemp contains a much higher volume of CBD when compared to marijuana. Additionally hemp contains no THC (the psychoactive cannabinoid in marijuana) making it legal to farm and consume in the United States under the Industrial Hemp Act.
Hemp and marijuana both fall under Cannabis and look similar however they are grown very differently.
Marijuana is grown specifically for its flowers and a lot of care is put into making the flowers (buds) as big and potent as possible. The value of the crop is dependent on it. Marijuana needs decent spacing between plants to ensure each plant can get as much light as possible to each flower. Marijuana requires a lot of attention to be successful.
Hemp on the other hand is grown more as an industrial crop, like corn. It is grown in mass. The plants are grown densely and the goal is a large bio mass. The hemp plant also has many valuable parts. From the flowers there is the extraction of CBD. The stalks and fibre are used in clothing, construction materials, paper, biofuel, plastic composites, etc.
Industrial hemp is a crop that can be grown inexpensively yet yields so much from all its parts.