A strain of cannabis is a unique genetic variety of the cannabis plant that has its own specific scents and effects. The best strains that are found among the cannabis plant varieties are bred and grown for years and decades. Popular strains become very well known. But strains also come and go, like trends.
A strain might be popular for years, and spawns many sub-species through crossing and hybridization, but then might lose popularity and become minor.
When you buy weed at a dispensary, you shop based on the strain. Each strain has a terpene profile, and a % of THC and CBD. Strains are usually classified by the plant’s classification of sativa, indica, hemp, or hybrid.