Polarized sunglasses work by filtering out some specific type of polarized light which reflects off of many smooth surfaces around us (glare). The glare light can be vertically, horizontally, or circularly polarized.
LCDs of all sorts produce almost exclusively polarized light from their liquid crystals. LCD displays as seen through polarized sunglasses will change in appearance as you rotate the lens (or instead your head) because the LCD light is polarized in a certain direction.
You can see this effect clearly by rotating the lenses of a pair of polarized sunglasses at right angles to each other. Since both lenses are perhaps horizontally polarized, one of them will then be vertically polarized and they will together block out almost all the visible light.
The new full color 3d movie technology (either at the theater, or at home) works by using two channels of circulary polarized light that are polarized in opposite directions. (As opposed to the old anaglyph red-blue system which produces 3d essentially in black and white by using color filtering)
Non polarized glasses just have a dark tint which filters all sources of light more or less equally.