Basic Regions 

Special or basic regions are common regions such as triangle, circle, and ball that have a special and convenient parametrization that makes them easy to specify. In the Wolfram Language, most graphics primitives are also geometric regions, and for Version 10 the number of primitives has effectively doubled. The basic regions extend beyond graphics to any number of dimensions and to exactly representing unbounded regions.

Basic geometric regions in 1D.

Basic geometric regions in 2D.

Basic geometric regions in 3D.

Basic geometric regions in D.