Vaporizers work by heating marijuana to just below the point of combustion, so that smoke is not produced. The user can inhale the marijuana without inhaling the noxious gases found in smoke. This has been very helpful for people who use marijuana medically in states where that is legal.
This method of using marijuana may be safer than other methods (such as smoking a "joint" or a "bong") in terms of the damage smoke can do to your lungs. However, using a vaporizer will not reduce any of the other potentially harmful effects of using marijuana.
Take a look at other questions on this website about marijuana. For more information on this, check out the answer to High Times. FX believes you would not have posted this question if you were not concerned about your health, and we want you to know that using marijuana, no matter how you do it, can present some short- and long-term side effects. If you ever become concerned about using drugs, we suggest talking to someone such as a teacher, a parent, a guidance counselor, a doctor or a school nurse. You can also call Marijuana Anonymous at 1.800.766.6779.