Imagi-nations are fictional countries, usually loosely based on historical countries of a particular time period. Ruritania from the Prisoner of Zenda is a good example, or consider Hollywood movies where (presumably to avoid offending a real nation) the story is set in some invented African or Middle Eastern country.
In wargaming the most popular setting for imagi-nations seems to be the 18th century, with modern Africa another popular choice. While I am tempted by the idea of making 18th century Cuties and will probably do so at some point, I chose to set my imagi-nations in the mid 19th century.
So, somewhere in Central Europe...
GrosseKleinStadt is based on Austria-Hungary, though much smaller in size. It is an old kingdom, its glory days long behind it, but it still has a large army though much of it is of poor quality. With a history of dominating its neighbours it has yet to accept it's reduced position in the world, which can lead it into wars it would have been better avoiding.
Bomenburst is more modern in its outlook. It models its army on that of Prussia, so while smaller in size than GrosseKleinStadt it is a serious threat to it. Constantly seeking to expand its influence and power, it all too frequently come so blows with its larger neighbour.
With two rival countries invented, I now have the choice of how much detail to go into. Maps must be drawn, cities named, troops cast, painted and organised into units. Significant people in both nations must be named, their personalities considered and possibly figures made to represent them. Perhaps most importantly, rules are needed to enable these countries to determine their fate on the battlefield.