According to a study published by the International Association of Plant Taxonomy in its article, a practical and natural taxonomy of cannabis, hemp plants and marijuana plants come from the same species of cannabis Sativa. However, the difference in their cultivation and growth would define the correct use that is each is given.
In this order of ideas, the term Marijuana is used when the Cannabis Sativa plant is specifically cultivated to obtain its maximum potential found in the resinous glands, known as Trichomes. These Trichomes contain high levels of Tetrahydrocannabinol concentration (THC). In other words, they contain a large amount of the component associated with psychoactive effects.
On the other hand, we refer to the term Hemp to the Cannabis Sativa plant that contains minimal amounts of the psychoactive component THC and is cultivated due to its variety of industrial and medicinal uses. Saying it in a metaphorical way, we could point to the marijuana plant and hemp plant as sisters who come from the same family Cannabis Sativa, and whose main difference is the psychoactive component which is greater than 0.3% in marijuana and less than that percentage in the hemp plant.