Navigation: How to Read Topographic Maps by Rob Richardson:
Topographic maps are created from aerial photography and satellite imaging; they describe the shape of the land, allowing you to see three-dimensional landscapes on a two-dimensional map. The maps define natural and manmade features like hills, valleys, vegetation, waterways, trails, bridges and roads. To be able to use these types of maps out in the wilderness, you need to learn how to read a topographic map. When reading a topographic map, you need to visualize a 3-dimensional view of what the symbols and contour lines on the map are showing.