and the volume is
This means that the torus surface is connected in the same way as the points on a rectangle, where you can “wrap-around” from one side of the rectangle to the other. This was a common topology used in the playing field of older video games.
The genus of a one-fold torus is 1.
Unusually, it is possible to divide a torus into seven different colored areas such that each area borders the other six. This is not possible on a flat surface or a sphere, where the maximum number of areas that can all touch each other is four.