To understand how 3D technology works; we must first understand how human sight works. Humans have two eyes approximately 3 inches apart. This distance creates two slightly different images. These images are transmitted to the brain and then the brain will create a space in where distance and depth can be perceived.
For 3D technology to create this same type of space in your brain, it needs to trick your brain into seeing two separate images from the same source. How 3D technology does this, is that it places two slightly different images over each other or in alternating sequence. The person must then wear a set of 3D glasses that will dissect this image and transmit it to the correct eye.
There are currently two types of 3D glasses technologies, active and passive. Active glasses have electronics that will change the display. Passive glasses have no electronics and use a different way to dissect the images.
Two of the currently used active 3D glasses technologies are liquid crystal shutter glasses and display glasses. Liquid crystal shutter glasses contain a liquid crystal that can block or pass light through in synchronization with the images on the display. It uses the concept of alternate frame sequencing which places the different frames in alternating order instead of over each other. Display glasses are head mounted stereoscopic displays. Each eye has its own display and they are slightly different then the other.
Two of the currently used passive 3D glasses technologies are linearly polarized glasses and circularly polarized glasses. Linearly polarized glasses uses two images that are superimposed over each other and the glasses uses an orthogonal polarizing filter to dissect the image. This technology requires the viewer to keep the head level because tilting of the head will cause the images to bleed over each other. Circularly polarized glasses use a pair of circular polarizers placed opposite each other. With this technology the viewer can tilt their heads left and right without the images bleeding into each other.