Ansel Adams invented the Zone System. It consists of Zone I to Zone X, whereas Zone X is pure white.
I learned in black and white photography by saying

Expose for the shadows; develop for the highlights.

However, the world of digital photography is very different. We want to expose for average color or Zone V, and check for highlight. Below is a color zone system which I created from researching. You used to put my camera in manual mode, spot meter, and use the color zone to meter how many f-stop need to make a good exposure. Photography after all is about lighting.

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To learn more about zone system, visit http://www.normankoren.com/zonesystem.html