Infrared is used for most security cameras. Day and night cameras have infrared LEDs that emit infrared light that only the camera can see. When it comes to day/night cameras range is everything. Cheap cameras will have weak LEDs that only emit a short light waves or that may have a lens/detector that can pick-up all of the infrared light being emitted. If you actually would like to see what is happening at night you will need to purchase a high-quality camera. Cameras that you purchase from your local electronics store are usually not of high-quality and will lack the LED strength or camera quality.