The defining difference between marijuana and hemp is the amount of THC. Marijuana refers to strains of cannabis that contain high levels of THC, often 10% or more. Hemp refers to strains of cannabis containing Non-Detectable THC. The same way apples have been breed over the years for some to be sweet and others tart, the Cannabis plant has been bred in different directions, one to increase the THC that gets you high, others (like the ones we use) to increase the other cannabinoids.