What 3D Glasses Do
3D glasses work by providing a separate image to each eye. The brain then combines the two images into a single image with 3D characteristics. The 3D process fools your brain into thinking it is seeing a 3D image, so it creates one for you.
3D-enabled TVs and 3D-enabled Video Projectors work by incoming 3D signal that can be encoded and sent in several different ways. The TV or projector has an internal decoder that takes the 3D signal and displays the left and right eye information on the TV screen in such a way that it appears to look like two overlapping images that look slightly out of focus.