Cannabis sativa is an annual plant in the Cannabaceae family. Humans have cultivated this herb throughout recorded history as a source of industrial fibre, seed oil, and food. Humans have long used the plant as a drug, as medicine, and as a spiritual tool. Each part of the plant is harvested differently, depending on the purpose of its use.

Cannabis Indica is an annual plant in the Cannabaceae family. A putative species of the genus Cannabis, it is typically distinguished from Cannabis sativa. Schultes described C. indica as relatively short, conical, and densely branched, whereas C. sativa was described as tall and laxly branched.[3] Anderson described indica plants as having short, broad leaflets whereas those of the sativa species were characterized as relatively long and narrow. Cannabis indica plants conforming to Schultes's and Anderson's descriptions may have originated from the Hindu Kush mountain range. Because of the often harsh and variable (extremely cold winters, and warm summers) climate of those parts, C. indica is well-suited for cultivation in temperate climates.

Marijuana strains are either pure breeds or hybrid varieties of Cannabis, typically of the species C. indica or C. sativa. Strains are developed to highlight a specific combination of properties of the plant or to establish marketing differentiation. Strain names are typically chosen by their growers, and often reflect properties of the plant, such as taste, color, smell, or the origin of the strain.
A strain may refer ambiguously to different forms of cannabis:

• Clone-only strain – A cannabis grower may grow a cannabis seed into a plant and find that this plant is unique in some way. The grower may make genetically identical clones of the plant and distribute these. A clone is the only way to propagate the exact genetic makeup that makes a strain unique, however, growing conditions greatly affects the plant and the final consumable product.

• Stable seed strain – For a cannabis breeder wishing to develop a new strain, the process is complicated and time consuming. It involves selectively choosing male and female cannabis plants and breeding them over the course of multiple generations. The final generation's seeds will have been stabilized by the breeder on the specific attributes chosen, though some genetic variation still exists among the seeds.

• Unstable seed strains – While these can be produced more quickly, plants grown from these seeds may have widely varying characteristics. Reputable seed shops will not distribute unstable seed strains, though some amateur growers might. Third-party growers may produce unstable derivatives from well known strains and misleadingly call them by their true strain name.

• Wild strains (Landraces) – Some strains, such as Columbian and Thai refer to cannabis plants found growing wild in certain regions. Typically, these plants are used as bases for the production of more specialized strains (e.g. G-13 or Haze).

Additionally, black market Cannabis dealers may distribute marijuana that is misleadingly called by a strain name. For example, Skunk and G13 may be used, but a lower grade may actually be sold. *From WikiPedia