Newtonian" refers to the OTA or Optical Tube Assembly; the actual telescope itself. It has a curved primary mirror at the back, a flat diagonal mirror at the front, and you look in through the front using eyepiece lenses. Newtonians can be put on any kind of mount. "Dobsonian" is the name that refers to a Newtonian placed on an altitude-azimuth rockerbox. All Dobsonians are Newtonians, but not all Newtonians are Dobsonians.