Also called "topo map" or "topographic map"; a type of
map which uses
contour lines and
elevation indicators to show the
shape of the region
depicted. Each contour line represents a set of spots having the same elevation, or height above (or below)
sea level. In a place where the ground
slopes steeply, the contour lines will be close together, and if the lines are far apart, that means the ground there is flatter. Topo maps will generally show
roads,
trails,
oceans,
lakes and
rivers; if the map is made to a sufficiently detailed
scale, it may show individual
buildings.
Topo maps are particularly useful when hiking and backpacking, and are indispensable for orienteering.
The United States Geological Survey has performed detailed mapping of all of the United States and US territories, and provides maps at many different levels of detail. Here's a web site that explains how to locate the right map and order it:
http://mapping.usgs.gov/mac/findmaps.html