Every object that has a temperature emits electromagnetic radiation. This includes radio waves, microwaves, X-rays and visible light, to name a few. The visible part of this spectrum includes the colours of light you are accustomed to seeing with your eyes. Many objects in the universe, both natural and man-made, emit or reflect visible radiation that allow you to see them.
A telescope is a device used to make objects that are very far away seem much closer. Telescopes collect visible light from distant objects such as the moon or distant stars, allowing astronomers to study them. They employ a system of lenses and mirrors to operate and come in sizes ranging from small backyard versions to large satellite-sized telescopes.
Many types of scientists utilise visible light that reflects from the surface of microscopic organisms to study their properties. A microscope makes a tiny object appear much larger, so that it can be categorised or tested.
Modern science has incorporated the visible light spectrum into many electronic devices in use today. Every device that has a viewable screen creates and emits visible light, which your eye perceives as a picture. Such technologies include MP3 players, touchpad devices, LCD computer monitors, cell phone screens and TV screens.