That handy-dandy, seldom-used-any-more phrase comes from the days when maps had East at the top instead of North. To make sure you were headed in the right direction, you turned east, holding the map, until things lined up. The sport of orienteering, lining things up and finding your way with only a map & compass, takes its name from that time, as well.
What does that have to do with writing, you ask? Well, take this scenario: You've written a book. The hero is driving south on Main Street, and suddenly, coming out from behind a cloud, the sun gets in his eyes, setting directly in front of him. Ummmm... Oops.
Maybe nothing this extreme has ever happened to you, but if you'll take the time to make a map of your book's main location, it won't ever have to! It doesn't have to be anything fancy, or rival the ones on the internet or in atlases. A few simple lines can keep you from having your character go out the door of the department store on First Street, having gone in the same door on Seventh Avenue.
I just "drew" a map of a town I've called Fictionville, using MS Paint. You don't need a computer program, although you could use a mapping program or a drawing program. Sometimes the simplest is the best. Try a pencil & paper, and just give yourself a rough idea where all the buildings in your setting are located. Here's my sample: