Positive/Negative Space
In a picture, the shapes that the artist has placed are considered the positive shapes. The spaces around the shapes are the negative spaces. It is just as important to consider the negative space in a picture as the positive shapes. Sometimes artists create pieces that have no distinction between positive and negative spaces. M. C. Escher was a master at creating drawings where there was no distinction between positive and negative space. Here is an example of Escher's work which show the interplay between positive and negative space: