All plant matter contain oils, flavors and other desired compounds. Examples include nicotine and terpenes in plants such as mint. Vaporization is the process of heating these compounds to convert them to vapor so they can be inhaled. It's the same thing as boiling. Typically, these desirable compounds boil at about 225-375 degrees Fahrenheit.
In conventional combustion smoking, the aromatherapy blends are burned and the heat from burning vaporizes the flavor compounds. But burning also creates toxic tar and carcinogens. The byproducts of burning are the most dangerous chemicals found in smoke. Fortunately, these byproducts are only created at temperatures above about 450 degrees Fahrenheit. So, if aromatherapy blends are heated to about 225-375 F, but no hotter, the desirable compounds are released, and the dangerous byproducts of burning are never created. That's vaporization. Vaporization is healthier, tastier and more pleasant than conventional smoking.