Coatings are thin layers applied to lenses and mirrors to enhance light transmission, protect mirror surfaces and suppress flare and color aberrations. See Importance of Coatings.
A finderscope is a small auxiliary telescope, attached to and aligned with the main telescope. It has low power magnification, a wide field of view and a crosshair to aid in centering. It assists you in finding and aiming at objects which you want to observe through the main telescope. Most finderscopes give an upside down or left-right reverse image.