The game is like a cross between Heroes of Might and Magic and Civilization. It's a turn-based 4X Game focused primarily on warfare, with tactical turn based combat (like XCOM).
You start by choosing a class and race for your leader, which will determine the units your empire can use. You start off with one city, but can gain more either through conquest, diplomacy, or by building them. You produce units and buildings in cities, and cost a money + time (i.e. this unit will take 50 gold + 2 turns to make).