I apologise for naming such a vast and relatively vague period of time, but I have been playing EU IV lately, and I was thinking about how horribly things can go wrong with so much information.
How did rulers "see" the world? How much information did they have on everything? What helped them make decisions, in terms of stats and maps? Or was most of it dealt with in a much more delegated sense?
A lot of what Medieval Kings in Europe knew about the world extended to Byzantium and the Near East. Jerusalem was placed at the centre of maps during the medieval period and the Crusades gave Medieval rulers exposure to the Muslim lands which surrounded it (Damascus, Jaffa, Acre, Damietta, Cairo, Alexandria, Antioch etc). They would have also been familiar with Ikonium and the lands of the Seljuk Turks because Byzantine leaders often had treaties with them. The Italian City states also had strong trading connections with all of these lands.
Beyond this, they new very little. They wrongly believed that there was a great Christian King - Prestor John in the world beyond - probably a rumour based on accounts of Chinggis Khan subjugating Muslims. A rumour that in fact cost them dearly on the Fifth Crusade as it likely influenced their decision to reject proposals for peace made by the muslim sultan Al-Kamil.
Another way they made decisions was with a heavy reliance on Classical teaching to give them an understanding of the history and geography of these places, which they called 'India', but which was actually what today we would consider parts of Africa and Eastern Asia. They thought these lands were inhabited by monsters and took the fantasies of the classical wold at face value. An example I can offer is the Friar William of Rubruck heading to the Mongol Court. He notes that upon 'inquir[ing] about the monsters and human freaks described by Isidore and Solius, [he] was told that such things had never been sighted.'
Sources: Jackson, Peter, 'Christians, Barbarians and Monsters: The European discovery of the world beyond Islam', in The Medieval World, ed. by Janet Nelson and Peter Linehan (London: Routledge, 2001), pp. 93-110
William of Rubruck, The Mission of Friar William of Rubruck: His Journey to the Court of the Great Khan Mongke, 1253-1255, trans. by Peter Jackson (Indianapolis, IN: Hackett Publishing Company, 2009)
Phillips, Jonathan. Holy Warriors: A Modern History of the Crusades (London: The Bodley Head, 2009)
Edit: Added an example
I recently read 1066 The Year of the Conquest by David Howarth, and he explains that people of that time did not think of geography in terms of maps, that is they didn't imagine a top down view, rather they thought of things from their point of view.
They might have imagined things as "beyond the forrest" or "over the hills". They would have known the directions but they wouldn't have imagined things in terms of a map.
Now, as cartography became better this probably changed, but early on they didn't have a lot of information.
Additionally he explains how news would travel from place to place. There were foreign nobles who would bring the latest news to court and town meetings that would bring new information.