The "Crudo" is kind of the western answer to Sashimi. The basic concept is the same.
You take a high-end cut of fish and "cure" it, using either/or a combination of vinegar, salt, and citrus.
Dishes such as ceviche, are almost always cured with lime juice or lemon juice.
The ingredients you use to cure the fish can be enhanced with herbs, citrus, various salts...etc...
The dish you see below is a scallop crudo, where I used a plum vinegar/salt cure. Served with various fruits and vegetables, and a roasted pepper "mustard" as the sauce.