Cannabis has been cultivated as an agricultural crop for over 10,000 years and used to support human wellness for over 4000 years. A PubMed search for cannabis finds over 15,000 research papers! (see here on PubMed)
Cannabis is a family of plants with two primary classifications — Indica and Sativa. While marijuana can be considered a member of either the Indica or Sativa families, Hemp is a member of the Cannabis Sativa family. Because Hemp and Marijuana both derive from the Cannabis Sativa family, they do share certain similarities; however, due to each plant’s biological structure, they have several very distinct and crucial differences. When compared side by side the two plants can each clearly be identified. The second significant difference between hemp and marijuana is the Tetrahydrocannabinol or THC content.
THC creates the psychoactive high or 'stone' related to marijuana. Hemp's THC content is neglible (<0.3%) while cannabis's can be very high! (Literally! with some strains reaching 40%).
Hemp traditionally has been primarily used for industrial purposes as it is capable of producing hundreds of important resources such as paper, clothing, building materials, biofuel, food products, oils and more.
Cannabis plants contain well over a hundred compounds called cannabinoids - the two dominant cannabinoids in cannabis plants are referred to as THC and CBD. According to Wikipedia, a cannabinoid is "a class of diverse chemical compounds that acts on cannabinoid receptors, AKA the Endocannabinoid system in cells that alter neurotransmitter release in the brain." These Endocannabinoid receptors that we have and our pets have in tissues throughout our bodies can accept cannabinoids that we and our pets produce naturally, or synthetic manufactured cannabinoids or cannabinoids produced in plants, like the cannabis plant and some other plants - these are called phytocannabinoids (phyto = plant origin)
Of the vast number of phytocannabinoids produced in the cannabis plants - two of the most dominant are Tetrahydrocannabinol (THC) type compounds (THC delta 9, THCVA, THCA etc) and Cannabidiol (CBD) type compounds (CBD, CBG, CBN, CBC, CBDA etc), as well as other active compounds like terpenes (beta caryophyllene, limonene and pinene to name a few) and flavonoids that are plant based antioxidants. Full spectrum hemp oil products can have a variety of CBD type compounds, terpenes and flavonoids (again zero to negligible THC so no 'high' or 'stone' effect).
Cannabinoids have been shown to provide profound benefits to human and animal bodies.
The presence of THC in Marijuana vs Hemp not only plays a huge role in how each plant is used, but it is also the defining factor in the legality of each plant. Each state/country will have varying laws based on the usage, sales, transportation, and cultivation of Cannabis. In most of the United States, the allowed THC-content for hemp to be classified as legal is 0.3%, while in much of the rest of the world, it is 0.2%.
Currently hemp oil products and marajuana products can not be sold in Canada without a special license however, hemp oil products (THC free) are legal to own in Canada and can be purchased and mailed to us from countries, like the U.S., which currently provide nearly half of the global market share of hemp derived CBD products.