Lox is a fillet of brined salmon, which may be smoked. Lox is frequently served on a bagel with cream cheese, and often garnished with tomato, sliced onion, cucumbers, and capers.
The traditional belly lox is known as such because it is made with a paper-thin cut from the fatty fish belly. Traditionally, the product is unsmoked and preserved by dry curing, leading to a very salty taste. Mass-produced lox generally use less salt and add cold smoke, making them more similar to a "Nova".
A Nova or Nova Scotia salmon, sometimes called Nova lox, is cured with a milder brine and then cold-smoked. The cut remains thin, making it a middle ground between the belly lox and regular smoked salmon. The name dates from a time when much of the salmon in New York City came from Nova Scotia. Today, however, the name only refers to the style of preparation and has no bearing on the source of the fish: they may come from other waters or even be raised on farms.
In contrast to lox, Scottish-style smoked salmon is rubbed with salt sugars, and spices as a dry-brine, which is then rinsed off and the fish is cold-smoked. Scandinavian-style gravlax is often made with a slightly thicker cut of fish, and immerses it in dill, sugar, spices, and salt to dry-cure it.