Night Vision Goggles (NVG) are specialized equipment that allow the user to see in low levels of light. They intensify already available light, such as the moon. The screen is colored green because humans can differentiate shades of green more easily than other phosphor colors.
NVG take up a Binoculars slot in the Inventory.
NVGs can also be used at night to penetrate heavy rain. For some reason, heavy downpour doesn't show up when wearing NVGs, allowing you to see even farther.
NVGs are often regarded as one of the most valuable and rarest pieces of equipment in the game. They can be found in Military spawns in Barracks or at heli crash sites and at some rare points it can spawn in found vehicles.