O-nigiri, also known as o-musubi, nigirimeshi or rice ball, is a Japanese food made from white rice formed into triangular or cylinder shapes and often wrapped in nori (seaweed). Traditionally, an onigiri is filled with pickled ume (umeboshi), salted salmon, katsuobushi, kombu, tarako, or any other salty or sour ingredient as a natural preservative. Because of the popularity of onigiri in Japan, most convenience stores stock their onigiri with various fillings and flavors. There are even specialized shops which only sell onigiri to take out. Due to its popularity in Japan, the trend of small restaurants and convenience stores selling onigiri has traveled to other parts of the world, such as Taiwan, China, Hong Kong, South Korea, Thailand, Switzerland, Hawaii, New York City, London, Australia, Canada, and parts of California.
—Onigiri from Wikipedia, the free encyclopedia