Conventional reflecting telescopes are a poor choice for terrestrial observation. You look into the scope, near the front, at a right angle. Catadioptric telescopes combine mirrors and lenses to give the light-gathering ability of a large mirror combined with a compact size. Eyepieces or cameras are at the back of the scope. A variation of this is the Maksutov Cassegrain design, such as the Meade ETX .
Astronomical telescopes make upside-down images .
Objective diameter - how big around is the lens that lets in the light, or the mirror that gathers light. For serious use, any telescope with a diameter less than 60mm is unacceptable. The quality isn't determined by the diameter, but manufacturers don't bother making good small-diameter eyepieces. Eyepiece focal length. The shorter the focal length of the eyepiece, the more magnification provided - but that leads to loss of sharpness and brightness.