Fm-3m is rock salt, copper and most of the simple metals, and its general multiplicity is the largest in the tables. Exercise 25 of 29, checked as you type.
Molecular point groups with their operations and character tables, the 230 space groups with a cell builder, and the 17 wallpaper and 7 frieze groups drawn live. The tool needs JavaScript, and WebGL2 for the 3D views; these are the pages it offers: