Answer:
A compass is a great tool for navigation because you can use it by itself to head in a straight line or just know what direction is which. If you use a map with a compass then you can use triangulation. This is where you orientate the map and then find three points and draw a line from them towards you based on their direction from the compass. This will tell you where you are and from this you can determine the direction to travel. All of this though was replaced with the invention of the GPS. This is a link about triangulation but they have images which might help understand better http://www.ussartf.org/compass_basics.htm.