"F6" is the keyboard function key used in the free-to-play game C-evo to display in a pop-up window a series of charts showing - with lines in the nations' colors - statistics of all nations you know about, from the year 4000 BC to the current year: Population, Territory, Military Power (somewhat restricted), Technology, Exploration, Cultivation. Too see the successive charts, click the "cycle" icon at top left or click F6 repeatedly. Some of the same information can be found in numerical form at F9 (C-evo), fairly useful if you find the chart colors difficult to distinguish.