A Chevrolet Cobalt starter motor is a fairly standard-looking automotive starter. It's roughly cylindrical, about 6-8 inches long and 3-4 inches in diameter (estimates vary slightly depending on engine size and year). It's typically made of metal, usually dark gray or black, and will have several large electrical terminals (one thick positive, one thick negative, and possibly a smaller terminal for a solenoid connection). It will also have a mounting bracket, either integrated or separate, to bolt it to the engine block. It might have some cooling fins on its casing.
There isn't a unique, easily identifiable visual characteristic that sets a Cobalt starter apart from other similar-sized starters for other vehicles. The best way to be sure is to consult a parts diagram or look up the part number for your specific year and engine. A picture search for "Chevrolet Cobalt starter" on Google Images will give you a visual idea, although appearance can vary slightly depending on the supplier.
