A strain's biochemical makeup comes from its genetic lineage and cultivation environment, and is often referred to as a cannabinoid profile. The difference in cannabinoid profiles is responsible for the difference in effects between strains.
A cannabinoid profile is a distinct ratio and concentration of cannabinoids. There are more than 70 cannabinoids, however only some of them are in great abundance. For simplicity, the cannabinoid profile is often reduced to a ratio of just THC and CBD.