Physically, each sailor who served in the ship will wear a campaign medal or ribbon for each area served in, such as the "Asiatic-Pacific area" for all activities in the Pacific War. The battle stars are 3/16 inch (5 mm) in diameter and bronze or silver, the silver equivalent to five bronze stars, and worn in a row on the ribbon.
The regulations for all this originated in 1942, and define "areas" and "engagements" in detail, as well as what qualifies as "participation", by ships and by individuals (for instance, an individual might have been assigned to a ship but not yet reported on board). Even so, there is still sometimes confusion over who is entitled to wear which stars.