In addition to featuring a distinct lack of Americas, maps from the Middle Ages were not laid out the same way.
Unlike modern maps, older navigation charts didn't have North on the top, South on the bottom, and East and West on the right and left respectively. Rather, they put East on the map's highest point, meaning Asia was on the top of the map while Europe was on the bottom.
In order to use the chart correctly, individuals would have to hold the map so that Asia was on the top. Asia was known by Europeans as the Orient, which derives from a Latin word meaning East. As such, when you moved the map so it was facing the correct direction, you were "orienting" it.
Not all modern maps place North at the top of the map. For example, maps of the Arctic and Antarctic generally orient themselves around the poles, while maps of cities bordering a sea generally orient the sea on top.
Some maps explicitly reverse the common "North on top" orientation, placing South on top and North on bottom. These maps are known as reversed maps.
