Nauru raised its own flag for the first time on January 31, 1968, the day the island became an independent republic. Until then it had been under British administration and then a United Nations trusteeship, and the flag was the most visible part of setting up an identity separate from that history.
Reading the flag
The field is dark blue for the Pacific that surrounds the island. A narrow yellow stripe crosses the center, standing for the equator and for the path of the sun overhead. Below the stripe, near the hoist, is a white twelve-pointed star, one point for each of Nauru's twelve original tribes.
The layout works as a map. The stripe sits where the equator sits, the star hangs below it, and that is where Nauru is: a small island a short way into the southern hemisphere. The tribes named by the star are the island's pre-colonial social structure, and the design leans on that rather than on anything inherited from the administering powers.
Where it flies
The flag is flown at government buildings and public ceremonies, and it represents Nauru at the United Nations and in regional forums. Handling follows the usual international conventions. There are no separate ceremonial or military variants.
References
[1] Republic of Nauru Government: Official Information (naurugov.nr)
[2] North American Vexillological Association Archives