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:

[Cylinder glued]

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

[Cylinder glued to rolled] ... a cylinder!

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

[Torus glued to rolled] ... a torus!

Excerpt from the Encyclopedia Britannica without permission.