A vaporizer is a device, either electric or portable, that extracts the active compounds from dried herbs so that they can be inhaled directly or stored in a "balloon". The resultant vapour looks a bit like smoke but doesn't contain tar or noxious, toxic gasses. It's simply the active ingredients forming a 'cloud' of potent vapour. When all the active ingredients have been extracted from the herb, you're not left with ashes, but dried up, odourless and colourless crumbs. Vaporizing is a clean, tasty and healthy alternative to smoking.
There are two main types of vaporizers. In one type the herb is placed on a small metal plate that is heated (conduction), and in the other type, a flow of very hot air is directed through the herb (convection). Nowadays most vaporizers are of the second type because, in the former, the herb might still get scorched, producing smoke rather than vapour.
In recent years, the market for portable vaporizers has expanded significantly. Development in battery technology has led to these vaporizers becoming more and more powerful at increased portability. Good examples of this are the Arizer Solo and DaVinci.
See the vaporizer section for an overview of the various pocketable and tabletop models.
For more information on vaporizers and their benefits, see: Vaporizer-info.com
For scientific data, see: Medical application of a vaporizer