Balance is the arrangement of visual weight in a composition. Every object in a composition has visual weight. Heavier objects cause your eye to gravitate towards them. When a design is unbalanced, one object may hold your attention captive. Your gaze might even fall right off the page. A balanced design allows your eye to comfortably flow across all objects on the page.
Many properties affect the visual weight of an object, including size, color, texture, shape, position, and contrast.