Gravlax is a Nordic dish consisting of raw salmon, cured in salt, sugar, and dill. Gravlax is usually served as an appetizer, sliced thinly and accompanied by hovmästarsås (literally steward sauce, also known as gravlaxsås), a dill and mustard sauce, either on bread of some kind, or with boiled potatoes.
During the Middle Ages, gravlax was made by fishermen, who salted the salmon and lightly fermented it by burying it in the sand above the high-tide line. The word gravlax comes from the Scandinavian word grav, which literally means "grave" (in Swedish, Norwegian, Danish), and lax (or laks), which means "salmon", thus gravlax means "buried salmon".
Today fermentation is no longer used in the production process. Instead the salmon is "buried" in a dry marinade of salt, sugar, and dill, and cured for a few days. As the salmon cures, by the action of osmosis, the moisture turns the dry cure into a highly concentrated brine, which can be used in Scandinavian cooking as part of a sauce. This same method of curing can be used for any fatty fish, but salmon is the most common.
Gravlax can be cured with salt, dill, beetroot  and is often eaten on Rye Bread 
Commercially prepared gravlax is sometimes smoked, and as such is incorrectly termed "gravlax".