Infrared is energy with a longer wavelength than visible light, existing just outside the range of human vision. The sun is a natural source of infrared energy, as well as many other forms of energy from across the electromagnetic spectrum. Flames also produce infrared, frequently putting out more infrared waves than visible light.
Infrared lamps are often used as heating aids in applications where a steady, low heat is required. However, these can also be used to illuminate an area with infrared. Infrared goggles can detect natural sources of energy, but an infrared light can provide enough reflected energy to create a clear picture of the user's surroundings. This allows someone using infrared technology to see a scene as clear as in daylight without providing any visible light. Infrared detection systems are also used to guide missiles toward enemy vehicles, whose engines give off large amounts of infrared energy.
Infrared technology is also used in remote control devices. An infrared remote sends out a modulated beam of infrared light, switching it on and off in pulses to communicate with other devices. A receiving photodiode in the controlled device can identify the infrared signal among the background infrared produced by visible light sources and decode the commands.