CBD oil is made by extracting all the phytochemicals from the entire cannabis sativa plant, including flower, leaves and stems.  This process captures all the cannabinoids, terpenes and essential oils found in the plant.  This allows them to work in harmony and is commonly known as the entourage effect.
Hemp oil on the other hand is derived strictly from the seed oil and does not use any other part of the plant.  While hemp oil has its benefits with the essential oils it contains, it has no CBD, terpenes, THC, or any other cannabinoid.  Hemp oil products can be found on Amazon whereas CBD products cannot.