Wikipedia: Telescope

Those telescopes in which the primary light-gathering surface is a lens are called refractive telescopes, those in which it is a mirror are reflective telescopes. The sensitivity and angular resolution of a telescope is determined to a great extent by the area of this light-gathering surface, termed it's "aperture". Because of the difficulty involved in manufacturing and manipulating large-aperture lenses, nearly all large research-grade astronomical telescopes are reflective telescopes.

The current generation of telescopes being constructed have a primary mirror of between 6 and 8 meters of diameter (for [ground based telescope]?s).

Refractive telescopes are similar in basic design and function to microscopes, and have with them a shared history.

The word telescope alone usually refers to optical/infrared/ultraviolet light telescopes, but there are telescopes for most of the spectrum of electromagnetic radiation For example, there are radio telescopes, which are essentially highly focused radio antennas, x-ray telescopes, gamma-ray? telescopes, etc.