A rice ball shaped triangle or bale shaped is called omusubi or onigiri in Japanese, and they are exactly the same food. The name onigiri comes from the Japanese verb nigiri, which means to grab or hold with one’s hands. Omusubi comes from the verb musubu which means to connect something. Both words mean to connect one thing with many things. Therefore, the meaning of onigiri is to make a ball by holding each grain of rice with your hands.
There are infinite variations of onigiri filling. The traditional ones are with grilled salmon (my favourite!) and umeboshi (pickled plums) are the most common. This shio musubi has no ingredients, just salt (shio in Japanese). Simple is best. Since it is only salt, it goes well with any dish. Choose your favorite salt and enjoy the simplicity.