CO2 extraction is one of the most common ways CBD is extracted from the hemp or cannabis plants. This method uses expensive equipment that adjusts temperature and pressure to extract the cannabinoids from the plant material, without damaging them. The other common method is to use solvents like ethanol or butane to extract the plant material. These solvents have to be burned off the final product which may damage the cannabinoids or terpenes in the process. There is also a risk that these solvents may not have burned off completely and could end up in your end product.
As is the case with any plant that constitutes a crop, cannabis plants have been selectively bred over the years to bolster one or another desired characteristic. This means that some plants provide a more potent psychotropic effect, others possess more prominent seeds (used in the production of cooking oil traditionally), while others may make for sturdier textile fibers.