Contrast is one of the most powerful design concepts of them all because really any design element can be contrasted with another. You can achieve contrast in many ways—for example, through the manipulation of space (near and far, empty and filled), through color choices (dark and light, cool and warm), by text selection (serif and sans serif, bold and narrow), by positioning of elements (top and bottom, isolated and grouped), and so on.
Making use of contrast can help you create a design in which one item is clearly dominant. This helps the viewer “get” the point of your design quickly. Every good design has a strong and clear focal point and having a clear contrast among elements (with one being clearly dominant) helps. If all items in a design are of equal or similar weight with weak contrast and with nothing being clearly dominant, it is difficult for the viewer to know where to begin. Designs with strong contrast attract interest, and help the viewer make sense of the visual. Weak contrast is not only boring, but it can be confusing.