Read a map key to interpret what symbols on a map represent.
A map cannot fit a real tree or a real building onto a piece of paper, so it uses symbols instead -- small pictures or shapes that stand for real things. A blue wavy line might mean a river. A green triangle might mean a park.
A map key (also called a legend) is a small box on the map that tells you what each symbol means. Always check the key first, because different maps can use different symbols.
Mastery looks like: They can use a map key to correctly identify what several symbols on a map represent.
Common stumbles: Guessing what a symbol means without checking the key, or assuming all maps use the exact same symbols.