Topographic maps are incredibly detailed maps which provide information about the physical features of the Earth. Technically, a topographic map includes both man made and natural features, essentially encapsulating all of the visible features in a region on paper. Since topographic maps are so detailed, a single map often covers a relatively small area, to ensure that no details are left out. Topo maps, as they are colloquially called, are extraordinarily useful in a number of fields.
The science of topography is quite old. Humans have been observing and cataloging the landscape around them for centuries, and converting this information into useful and concise maps. Maps help people figure out where they are, and they can be used to put land into context, since they abstract a region and allow people to essentially observe it from above. The United States Geological Service, among many other organizations, has devoted a great deal of time and energy to topography and the publication of topographic maps.
Most people recognize a topographical map by the characteristic contour lines. Contour lines connect points of the same elevation, creating a two dimensional representation of three dimensional space. Each contour line represents a different elevation, with close-set contour lines indicating a steep region of the Earth, and broad contour lines suggesting more gentle terrain. When contour lines are used in a body of water, they are referred to as bathymetric contours. The map is also usually shaded to help people identify forests, towns, and so forth, and features like rivers and roads are clearly outlined as well.
Some people call topographic maps contour maps, in a reference to the lines which distinguish a topo map. A contour map could also be shaded to create a clear relief map. However, good topographic maps also have information about structures and major noticeable landmarks, making them about much more than just elevation and steepness. Such a map might, for example, have a grayed out area representing a town, with black squares indicating buildings. Features of note are often labeled, so that someone can look at a map and find things like fire towers or churches. These features can be used to orient the map user in the real world.
Hikers, naturalists, and geologists all rely on topographic maps to get around in the field. People who practice orienteering often find the maps useful, as well. Topographic maps may also be used in cultural analysis, demonstrating, for example, that early settlers in a region clearly chose regions of more even elevation, or that a neighbor on steep land sued another for his or her more even, easily worked land.