Tuna, octopus, prawn, squid and salmon roe are common sushi ingredients. They could all be raw. Octopus, prawn and squid can be cooked and cooled. If you are eating them raw, you have to buy those ingredients, specifically sold to be eaten raw. Otherwise, you might get food poisoning.
"Sushi" can include sushi rolls (with dry seaweed) but usually it refers to sushi rice firmly shaped into a long, oval form with a piece of sliced fish on top of it (more specifically nigiri-zushi). Sushi rolls are usually called norimaki (rather than "sushi" although it is a type of sushi). Sashimi usually refers to raw fish by itself without rice.