Salt has always been present in all civilizations. The history of salt is closely related to human history, simply because it is essential to our survival. That is why we have always sought ways to produce it industrially. As a rare commodity, salt has always been the subject of intense trade, a source of revenue for governments that tax it, and the cause of wars and revolts, the latest being, in 1930, the Salt March, led by Gandhi to protest against the monopoly held by Britain.

Since prehistoric times, salt has been harvested empirically either on the edges of the coasts of warm seas or from salt-rich earth. In China, salt from Lake Yüanchang, a salt lake, was produced more than 6,000 years ago. Two millennia later, they salted fish and meat there. In North America, when the first settlers arrived, they found that indigenous people were extremely skilled in harvesting salt from both the sea and earth. In Europe, the first true salt marshes were developed by the Romans.

However, since it was not found everywhere, salt has always been the subject of intense trade. The "salt roads" have been, since ancient times, the main lines of communication between countries.

Salt preservation was perfected by the Romans, who used this method to preserve meat, fish, and vegetables. It was, in fact, a major reason for the success of their conquests as the armies never traveled without supplies of salt and salty foods.

It was also used as a currency called salarium, which is the origin of the word "salary".  In France, it was subject to a special salt tax, the gabelle, which was much more unpopular than VAT, and which led to many revolts. Established in 1341 by Philip VI, it remained in force for over 400 years until it was abolished during the Revolution. During this time, gabelle had been the largest source of revenue for successive monarchies. In Paris, there were a few salt storehouses, but they were rife with fraudulent trading and contraband.

As it was so rare and precious, in many cultures, salt was (and still is) considered holy. It is present in several religions, considered at different times and in different civilizations as a gift from God, or capable of exorcising demons and chasing away misfortune. There are still many rituals and turns of phrase involving salt.

In Mediterranean countries and Japan, offering salt was a gesture of hospitality and honor, and so created an unbreakable bond. If salt was spilled, this was a sign that the bond was broken, and that misfortune was around the corner.

The composition of dietary salt is set by the International Codex Alimentarius. The dry weight (without any water residue) must contain a minimum of 97% sodium chloride (the chemical formula of salt).

Coarse salt is sold in bags of 1–10 kg.

Fine salt is sold in boxes of different weights.

Special salt varieties are usually packaged in small bags or bottles.

Most of the cooking salt produced goes to the food industry for the manufacture of various products requiring salt: cold cuts, smoked fish and meats, cheeses, breads, biscuits, sauces, and ready meals, etc.

It is clear that salt is the basis of good seasoning and that it must be measured accurately. Too much can completely destroy the best dishes, while too little is no less damaging to the taste.

The type of salt chosen depends on its use in a dish.

Coarse salt is also used as a cooking method in which fish or poultry are enclosed in a "salt crust", i.e. a thick amount of coarse salt mixed with a little flour or seaweed.

As salt is very hygroscopic, tending to absorb moisture from the air, it is essential to always keep it in a dry place, in a tightly sealed container.

Salt is composed of two molecules, chlorine and sodium, bonded together to form sodium chloride (NaCl). 1 g of salt contains 400 mg of sodium, which is required by the body as it controls, along with potassium, the water balance of the body using very complex biological mechanisms.

The body's requirements in sodium chloride are estimated at between 2–4 g per day. Most people consume more salt than they need, ranging from 8–15 g per day.

This excess in sodium is thought to be a major contributing factor to high blood pressure, which is why there are so many campaigns to encourage individuals to reduce their salt intake to no more than 6–8 g per day, and food manufacturers to use less salt in their products.

Unrefined gray sea salt contains small amounts of minerals that are often praised for their nutritional qualities. However, given the small quantities actually consumed, these qualities have absolutely no effect on the diet. In other words, from a nutritional point of view, this salt is no "better" than refined white salt.