The most common form of patent protection is a utility patent that covers the changes that make a product or service more useful or better using science or engineering. (Note--a utility patent is often just called a patent as this is the most common form of patent).
A separate type of patent protection is a design patent. A utility patent describes and claims the “what” and the “how”. In contrast, a design patent has a focus on the ornamental appearance of an object. One way to think of “ornamental” is “not required”. Some aspects of a design are required (a tire needs a hole in the middle for the wheel) but many aspects can be done in a variety of ways. The combination of these not-required features is the way that a consumer can recognize that a product comes from a specific source even without reading the label. Thus, a design patent is somewhat like a trademark in that it helps consumers buy a product from a specific source without getting confused by knockoff products. The test for infringement a design patent can be stated as whether the claimed design is substantially the same as the accused product in light of the prior art.
Design patents are often particularly useful in consumer products that are purchased without a great deal of investigation (impulse buys). Design patents can be useful to help protect disposable products that are used with a patented device but lack strong utility patent protection for the disposable products. Sometimes a client will protect portions of a device likely to need replacement with design patents. An example would be obtaining a design patent on the front grille of an automobile so that the manufacturer can prohibit companies from making look-alike replacement grilles for the repair industry.
Design patents may be used to protect distinctive icons used in graphic user interfaces (GUIs) on computer screens or smartphones. The design patents may include dynamic sequences or static images. Design patent disputes played a central role in the recent patent battles between Samsung and Apple with respect to smartphones.