Nigiri sushi (sometimes nigirizushi) are just one part of a large selection of foods. Sushi is the sticky, short grained rice, that is seasoned with sushisu (usually rice vinegar, sugar but sometimes mirin, and salt). It can be rolled in a seaweed wrapper, nori. to make a sushi roll, a makizushi. Sushi rice can be served as a small dollop of rice with seafood or any number of other toppings and is called nigiri sushi.
The first time you make a selection of sushi, it will seem all too complicated, work intensive and time consuming. That’s just the learning process. The second time you make your sushi you will be amazed at how much easier it was than you remembered. By the third or fourth time, you will be able to make sushi without giving it a second thought.
There are traditional sushi selections but the choice of ingredients to complete your nigiri sushi is up to you and your individual taste.