"Dobsonian Telescopes" is a sort of misnomer. It is a term used to describe a Newtonian reflector telescope on a Dobsonian Mount. The Dobsonian Mount is an alt-azimuth base mount and is a sort of a rocker-box-on-a-lazy-susan. It is the least expensive way to get into a large aperture telescope - All the money is spent on the primary mirror.

The Dobsonian Mount was popularized by John Dobson, who is one of the co-founders of the San Francisco Sidewalk Astronomers. For a more information one this usually influencial and interesting Astronomer click here to read his biography on Wikipedia.com.