The passage of the Agricultural Improvement Act of 2018 establishes a marked shift in United States federal policy toward the cultivation and utilization of hemp, while distinguishing it from the drug varieties of cannabis [1]. As farmers begin to cultivate hemp, as herbalists begin extracting its constituents, and as patients and consumers begin ingesting these extracts, we must ask: “What is hemp?” The distinctions between true agricultural hemp and drug-type cannabis plants (i.e., marijuana) extend beyond legal importance. In this chapter, the botanical, genetic, agricultural, and phytopharmacological characteristics of this plant will be discussed.