3-D glasses work by filtering the light that reaches each eye so that the brain receives two slightly different images. The brain then combines these images to create a single, three-dimensional image.

There are two main types of 3-D glasses:

* Anaglyph glasses use colored filters to filter the light that reaches each eye. The most common type of anaglyph glasses uses red and blue filters. The red filter allows only red light to reach the left eye, while the blue filter allows only blue light to reach the right eye. When the brain combines these two images, it creates a 3-D effect.

* Polarized glasses use a different type of filter to separate the light that reaches each eye. Polarized glasses have a series of thin slits that allow only light waves that are vibrating in a certain direction to pass through. The slits in the left and right lenses of polarized glasses are oriented at right angles to each other, so the light that reaches each eye is polarized in a different direction. When the brain combines these two images, it creates a 3-D effect.

There are also two main types of 3-D displays:

* Stereoscopic displays use two projectors or monitors to display two slightly different images, one for each eye. The viewer wears 3-D glasses that filter the light so that each eye sees only the image that is intended for it.

* Autostereoscopic displays use a special type of screen that allows the viewer to see two different images without wearing 3-D glasses. This type of display is often used in portable devices, such as smartphones and tablets.

3-D technology is constantly evolving, and new types of 3-D glasses and displays are being developed all the time. As 3-D technology becomes more affordable and accessible, it is likely to become more common in a variety of applications, such as movies, television, video games, and virtual reality.