Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.
Mail pouch
Domestic mail that would be carried in a mail pouch is mail that would be ultimately delivered to United States territories and possessions ("e.g.", Army Post Offices (APOs), fleet Post Offices (FPOs), and the United Nations, NY). The United States Postal Service defines "territories and possessions" in its Domestic Mail Manual (DMM) as being American Samoa, Manua Island, Swains Island, Tutuila Island, Guam, Northern Mariana Islands, Commonwealth of the Rota Island, Saipan Island, Tinian Island, Puerto Rico, U.S. Virgin Islands, St. Croix Island, St. John Island, St. Thomas Island, Wake Atoll, and Wake Island. Mail originating in the United States and going to or coming from the Freely Associated States is treated as domestic mail. These are the Marshall Islands, Ebeye Island, Kwajalein Island, Micronesia, Kosrae Island, Pohnpei Island, Yap Island, Palau, and Koror Island.