Composition in the visual arts often relies on the arrangement of formal elements, known as: line, shape, space, color, light, texture and pattern. In any work of art, at least two or three of these formal elements take precedence. For example, Ingres is particularly famous for his lyrical use of contour lines (lines that follow the curvature of a three-dimensional shape).
Many works of art feature a focal point in a particular part of the painting. Often artists and designers emphasize one thing by making it bigger than the surrounding objects, or using lines and shapes to direct the viewer's eye to a particular part of the composition or using a different color or value to make one part of the painting pop out from the rest.
However, there are several artists famous for their refusal to give the viewer a focal point, among them Jackson Pollock, Agnes Martin and Sol Lewitt.
Unity refers to the degree to which the elements of the painting combine to form a single object, a unified composition. While a blank white wall may be unified, there is not much visual interest--but were the artist to hand out crayons to a group of people and ask them to draw anything on the wall, there would be variety but little focus. Most artists and designers work in between the extremes of total unity and total variety.
Artworks that are balanced tend to be symmetrical--each side of the composition echoes the other, creating a sense of stability in the work.
Unbalance results when the composition is asymmetrical--one side may be a wildly different color, or may contain a larger shape, or have more variety than the other and so forth. Unbalanced compositions tend to create a sense of strain in the viewer, which is sometimes a desired effect.