The document provides an overview of how telescopes work, including their history and the key components and principles of refracting and reflecting telescopes. Refracting telescopes use lenses to bend light rays and form an image, while reflecting telescopes use mirrors. Both collect light and use additional lenses or mirrors to magnify the image for viewing. The size of the objective lens or mirror determines how much light is collected, while different eyepieces allow changing the magnification. Filters can enhance viewing of certain objects. Modern telescopes also observe wavelengths beyond visible light.