A telescopic sight, commonly called a scope, is an optical sighting device that is based on a refracting telescope.
They are equipped with some form of graphic image pattern (a reticle) mounted in an optically appropriate position in their optical system to give an accurate aiming point.
Telescopic sights are used with all types of systems that require accurate aiming but are most commonly found on firearms, particularly rifles.
Other types of sights are iron sights, reflector (reflex) sights, and laser sights. The optical components may be combined with optoelectronics to form a night scope.