In terms of the difference between Hemp and CBD. Hemp is a strain of the cannabis Sativa plant species and contains 0.3% (or less) THC. CBD is one of the hundreds of components in the hemp plant. Hemp has been used for centuries as an industrial material for textiles. CBD - short for Cannabidiol - can be extracted from both hemp and cannabis.  

Hemp-derived CBD is produced from industrial hemp plants, often harvested for their stalks and seeds.

Many people believe that cannabinoids have therapeutic benefits, especially as they specifically target and influence the endocannabinoid system, present in all humans.