You have two eyes so that you can sense 'depth' when you look around you. Each eye sees a slightly different image and your brain can analyze the differences to estimate how far away things are. With a 3D program like Blender we can produce pairs of images to give your eyes the same impression of depth when your eyes sees the pair of images, but what is the best way to ensure that each eye sees the correct image? Several solutions are possible and are explained on a page that you can access via THIS LINK. One solution, the theme of this page, is to create a combined image called an anaglyph in which one of the original images is present only in red and the other is present only in cyan (blue and green). If the viewer wears special glasses with a red filter over the left eye and a cyan filter over the right eye then the left eye will see only the red image and the right eye will see only the cyan image. So don't bother reading any more of this page unless you can obtain the necessary pair of (very cheap) glasses, like this (from Amazon, Ebay etc):
A nice addon is available for free download which, once installed in Blender, makes it rather easy to generate your own anaglyph images. Here is an example of an anaglyph made with the addon (yes, it's time to put your red-cyan glasses on):
This below is the same image without the 3D effect:
This is the 3D viewport view which shows the three planes. Note that the three monkey heads are almost completely between the near and far planes.
The three planes do not show up in the final rendered view (F12) but they are visible in the 'live-rendered' view:
Here is the procedure for installing and activating the addon (this is not necessary at school for it has already been done)
Here is the procedure for using the addon that have installed as above
Lastly, note that anaglyphs can be used to made 3D movies, not just still images. See the excellent 10 minute anaglyph movie 'Pangea, the never-ending world' on YouTube, for example.