The difference between hemp and CBD comes down to the cannabinoid content. Cannabinoids are beneficial plant compounds, including THC, CBD, and others. Both hemp oil and hemp-derived CBD products are legal and contain less than 0.3% THC, the psychoactive cannabinoid found in marijuana.
CBD oil is the isolated extract of a single cannabinoid, cannabidiol (CBD). Hemp oil is a whole-plant extract that contains all of the cannabinoids, including, but not limited to, CBD. When taken together, cannabinoids have a synergistic effect, called the entourage effect.
If you are looking to reap the benefits of the entourage effect, you should try full-spectrum hemp oil. If you are concerned about THC, even in small amounts, you should try CBD oil or broad-spectrum hemp oil.