Nigiri (握り寿司, “hand-pressed sushi”) consists of an oblong mound of sushi rice that the chef presses into a small rectangular box between the palms of the hands, usually with a bit of wasabi, and a topping (the neta) draped over it. Neta are typically fish such as salmon, tuna or other seafood.
Gunkan (軍艦巻, “warship roll”) is a special type of nigirizushi: an oval, hand-formed clump of sushi rice that has a strip of nori wrapped around its perimeter to form a vessel that is filled with some soft, loose or fine-chopped ingredient that requires the confinement of nori such as roe, nattō, oysters, uni (sea urchin roe), corn with mayonnaise, scallops, and quail eggs.
Hosomaki (細巻, “thin rolls”) is a small cylindrical piece, with nori on the outside. A typical hosomaki has a diameter of about two and a half centimeters. They generally contain only one filling, often tuna, cucumber, kanpyō, thinly sliced carrots, or, more recently, avocado. Kappamaki, (河童巻) a kind of Hosomaki filled with cucumber, is named after the Japanese legendary water imp fond of cucumbers called the kappa.
Chirashi (ちらし寿司, “scattered sushi”) is a bowl of sushi rice topped with a variety of raw fish and vegetables/garnishes (also refers to barazushi). There is no set formula for the ingredients; they are either chef’s choice or specified by the customer. It is commonly eaten because it is filling, fast and easy to make. Chirashizushi also often varies regionally. It is eaten annually on Hinamatsuri in March.
Uramaki (裏巻, “inside-out roll”) is a medium-sized cylindrical piece with two or more fillings, and was innovated as a result of the creation of the California roll, as a method originally meant to hide the nori. Uramaki differs from other makimono because the rice is on the outside and the nori inside. The filling is in the center surrounded by nori, then a layer of rice, and optionally an outer coating of some other ingredients such as roe or toasted sesame seeds. It can be made with different fillings, such as tuna, crab meat, avocado, mayonnaise, cucumber or carrots.