What do the following terms designate: “metropolitan France,” also called “the Hexagon,” and “France as a whole”? What are the differences between them?

Statistical tables often specify that the figures in them apply to either “metropolitan France” or “France as a whole.”

The terms “metropolitan France” and “the Hexagon” cover all 96 départements (départements are French territorial administrative units) départements of mainland France and the two départements of Corsica (which, as an island in the Mediterranean Sea, is of cource not territorially contiguous with the mainland). 
The term “France as a whole” includes the country’s overseas départements and regions (DROMs): Guadeloupe, Martinique, French Guiana, Reunion, and Mayotte.

French statistical tables were first extended to apply to France as a whole only very recently, in the mid-2010s This is because long historical series tend to concern a relatively restricted population frame.

Some historical statistical series are disrupted by changes in the country’s borders. For example, in 1860, France annexed Savoie and the county of Nice. And from 1871 to 1920, the period following the Franco-Prussian War (1870-1871), France was without three of its départements: the Bas-Rhin (Lower Rhine), the Haut-Rhin (Upper Rhine) and Moselle.

It should be noted too that the term “France as a whole,” or simply “France,” does not encompass the set of administrative units called “overseas collectives” or COMs (geographic territories under local governments), the most important of which are New Caledonia and French Polynesia.