Value

Value is used to describe the lightness or darkness of a given area. For example

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Drawing by Marguerite Smith

Value can create emphasis. Using various values, a focal point will be established. Having something light on a dark background or something dark on a light background will create emphasis. 

Gradation of value can also be used to give a sense of depth. Light and dark areas can give the impression of being three dimensional. 

Value is the best Element of Design because of the different things it can be used for.

This is where I got my information from.