Setting circles tell you the celestial coordinates at which the telescope is aimed. They make it much simpler to locate stars, galaxies, and other celestial objects, much as an earthly navigator might locate a position on the earth using the familiar latitude and longitude coordinates. Once your telescope is properly in alignment with the celestial sphere, you can use the setting circle dials on your telescope to locate the coordinates found in a star chart or star atlas for the object you want to see. This way, you can even find objects too faint to be seen in the finder scope. It's a real surprise to most people to see how quickly even a large object like the Moon will drift right out of view, unless a motor drive is in use.
Motor drives come in many types, some plug into a regular power outlet, some are battery operated.
A power converter can usually switch one type to another. No other characteristic of telescopes is so widely known and yet so misunderstood by most people. The magnification of most telescopes is variable, depending on the focal length of the eyepiece being used. The eyepiece used is the 'gas pedal', and if you want to see any of the scenery, you won't often 'floor it'. As power increases, image brightness and sharpness decreases rapidly.