Anaglyphs are stereo pairs combined together in a single image and require a simple, cheap red/blue pair of glasses to see the image in 3D. (More on anaglyph 3D.)
ImageMagik combine -stereo was used to superimpose 2 separate images: one for the left eye and one for the right eye.

Glasses can be home-made (red on the left eye, Blue/Green on the right eye) or purchased in novelty stores, catalogs, and online.*