Binoculars are a human invention that originally utilized curved glass lenses to enhance and focus the light that reflects from far away objects. This of course only works for visible light. The more modern binoculars can be combined with cameras which can pick up light frequencies that the human eye cannot perceive and show these in visible light on an available monitor.
Two technologies that are based on the same principals are the scopes used on firearms and telescopes which also use mirrors in combination with the lenses to increase the amount of incoming light.
Throughout the years SG personnel has been shown to use binoculars to spy on anything from birds to enemy Jaffa.
Another similar technology was incorporated into the helmet of Aris Boch which allowed him to zoom in on a wooded area further down a valley on the planet PJ6-877 while showing SG-1 the hiding spot of the Tok'ra Korra. (SG1: "Deadman Switch")