Infrared photography is a process that allows the camera to see infrared light, which we can't see. Infrared light is all around us, especially reflected off living foliage (leaves, grass, etc.) in direct sunlight. An infrared filter is used to sort the infrared light and the visible (regular) light. In my photography I utilizes the high-end of the reflected light infrared spectrum. Video infrared, made famous in police night chases, "sees" the lower end of the radiant infrared spectrum (or heat signature), thus "seeing" in the dark.