A torus is a mathethican's name for a dountnut. The surface of a torus is topological space found in most video games, where a spaceship goes off the right-hand side of the screen only to reappear on the left, or off the top to reappear on the bottom.

To illusrate life on the surface of a torus take a simple square with only one pair of edges glued with no flip:

The square can be rolled so that the two marked edges meet. The resulting shape would be...

If the top and bottom edges were also glued, then the shape in three dimensions would be ...

*Excerpt from the Encyclopedia Britannica without permission.*