If you live in a very
rural area, or in a place civilized enough to
outlaw wholesale light
pollution, you may not have ever seen it. It'd probably
disturb you if you did.
Picture a diffuse brownish glow in the sky, a gradient from brightest near the ground to darkest directly above your head. In the directions of large cities the horizon glows the most strongly, and in directions where there is no population, it may be as dark as the sky above. There are a handful of stars above you in the darkest places -- if it's winter you may even be able to make out the constellation Orion. Very few stars though, maybe one-hundred, nowhere near the crystalline infinity that you are used to. Certainly no galaxies or comets either; the closest thing you can find are a few airplanes and satellites.
Because of the extra light even the planets look the same color as the scant few stars, a dull white-on-brown. In deepest night, when all of the white lights have been turned off and only the orange sodium arcs remain, the glow takes on a horrid red tinge -- like the fires of hell burning somewhere not far away.
I don't look forward to telling my children what the stars were like.