They are those signals used in the maps that indicate something, and it gets its meaning in the legend.Depending on the map you'll find various types of symbols, but the most common is the rose of the winds, or pointed to the North, South, East and West. It is essential to move.If it is a map of a city, a plane, can contain icons that indicate bus stops, metro, places of interest, hotels, etc..In a road map indicated the type of road, if the road is secondary, is a highway...Maps often are concentric and closed curves called level curves, indicating the height of the terrain at each point ( it is reduced to doing 10 m 10 m, or 25 in 15, 100 in 100, according to the 41 scale;