Anaglyph 3D is the name given to the stereoscopic 3D effect achieved by means of encoding each eye's image using filters of different (usually chromatically opposite) colours, typically red (left eye) and cyan (right eye). Anaglyph 3D images contain two differently filtered coloured images, one for each eye. When viewed through the "colour-coded" "anaglyph glasses", each of the two images reaches the eye it's intended for, revealing an integrated stereoscopic image.

To view these images in 3D you will need a pair of red / cyan glasses which you can easily make for less than a $1 (plans can be found on the internet).