A space group is the symmetry group of a configuration in space. The space group describes the symmetry of a crystal. This search only applies to structures determined by crystallographic methods such as X-ray and electron crystallography. The elements of the space group fixing a point of space are rotations, reflections, the identity element, and improper rotations

the canonical definition for space group is something that i understand, but question here is about to understand how those images in the mentioned link explain different space groups (http://img.chem.ucl.ac.uk/sgp/medium/sgp.htm)