Position describes the relationship between a figure and the format in which it will function. Position can be described relatively, such as lower right corner or center, or described absolutely, such as two inches from left margin and three inches from top margin.

Position is a descriptor:

In this example, the square in the center becomes the primary figure within the sequence because of motion. The motion is a change of position, moving up and down. If you stop the movie at the beginning or end, there is no clear primary figure due to all three squares being fundamentally identical (except for different positions).