A topographic map, unlike a road map or atlas, shows a piece of land as it actually appears in real life. This means it not only shows roads, buildings and bodies of water, but gives the user an idea of the terrain of a certain area.
Contour lines are what allow topographic maps to show the terrain, or the rising and falling elevation of a certain piece of land. Usually brown in color, contour lines connect points of equal elevation. If the contour lines on a map appear close together, it signifies a steep ascent or decline in elevation, such as a cliff or ravine. If the lines are far apart, it signifies a gradual accent or decline.
A topographic map will have a key, usually in one of the corners of the map, that explains all of the symbols used on the map.
Declination is the difference between true North, or the North Pole, and magnetic north, located in Canada. You will have to account for this difference when using a topographic map with a compass.
Topographic maps are available in many camping supply and book stores. A great resource for topographic maps is the U.S. Geological Survey, which produces and sells topographic maps for the entire United States.