A marijuana vaporizer doesn’t burn your herb, it just heats it to a temperature where the good stuff, the cannabinoids; THC, CBD etc, and the terpenes; the taste and smell, are released. Many larger vaporizers blow hot air through the mix, and many portable vaporizers have a small “oven” that heats the herb directly.
A good vaporizer will give you the choice to set the temperature. Different heat levels will affect the taste and type of high you get from your vaporizer with the ideal temperature for vaporizing cannabis around 185°C (365°F).
It’s best to use a grinder and grind your weed up to make sure you it vaporizes evenly. The quality of your herb and the type of vaporizer you’re using will of course have a big effect on the quality of the vapor