Night Vision Monoculars, Night Vision Binoculars and Night Vision Scopes are electro-optical devices that intensify (or amplify) existing light instead of relying on a light source of their own. The night vision devices are sensitive to a broad spectrum of light, from visible through infrared. An accessory illuminator can increase the light available at the infrared end of the spectrum by casting a beam of light that is not visible to the human eye.

You do not look "through" a Night Vision product, you look at the the amplified electronic image on a phosphor screen.
Light enters the Night Vision device through an objective lens and strikes a photo cathode that has a high energy charge from the power supply. The energy charge accelerates across a vacuum inside the intensifier and strikes a phosphor screen (like a TV screen) where the image is focused. The eyepiece magnifies the image.

A Night Vision phosphor screen is purposefully colored green because the human eye can differentiate more shades of green than other phosphor colors.

Like cameras, Night Vision products have various image magnifications. The distance at which a human-sized figure can be clearly recognized under normal conditions (moon and star light, with no haze or fog) depends on both the magnifying power of the objective lens and the strength of the image intensifier. The maximum viewing range of the Moonlight product familty is from 200 feet to 800 feet.