Salt, or sodium chloride, is a mineral, one of the few that people eat. Saltiness is one of the basic flavors perceived by our taste buds, along with sweet, sour, bitter, and umami. Salt is required for life, but overconsumption can increase the risk of health problems, including high blood pressure. Salt can be reduced by 20% to 45% without compromising taste if a small amount of MSG is added to the food. Salt is also used to preserve food.
Salt has a long, varied, and sometimes violent history. It has been a highly valued trade item throughout history. Wars have been fought over it, states formed and destroyed because of it. During the late Roman Empire era and throughout the Middle Ages, salt was a precious commodity carried along the "Salt Roads" into the heartland of the Germanic tribes. Cites, states and dukedoms along the salt roads exacted heavy duties and taxes for the salt passing through their territories. This practice has caused wars, and it even started the formation of cities, such as the city of Munich in 1158 when the then-duke of Bavaria, Henry II, decided that the bishops of Freising no longer needed their salt revenue.
Types of salt 
For the most part, the various grades of salt are all the same; chemically most are greater than 99% sodium chloride, but the structure varies widely.
- Simple table salt consists of small, compact cubic grains, usually with iodine added .
- Kosher salt has a much more irregular structure, no iodine, and a larger surface area. Chefs prefer it for some dishes because of its texture and a seemingly "cleaner" taste from being without iodine.. The name comes its role in "koshering" meat: preparing it in accordance with Jewish dietary law (kosher).
- Popcorn salt/Canning and pickling is ground salt that dissolves very quickly and able to dissolve in cold fluid.
- Rock salt is large chunks of sodium chloride.
These differences in structure can cause a significant change in the perceived flavor of the salt and its usefulness for particular recipes. The speed with which it dissolves is also very important, with finer salts such as pickling salt even dissolving readily in cold liquid.
Table salt also contains anti-caking agents to allow it to flow freely, and sometimes contains very small amounts of iodine.
Sea salt, which is made from evaporating seawater, also varies considerably. Because there are impurities in the water, each sea salt has a unique taste and is prized in different cuisines or for different applications. Sea salts often tend to cost considerably more than other kinds of salt; however, in areas with large seawater evaporation industries (such as California) the "table salt" in local stores may actually be sea salt.
Salt comes from two sources, mining natural halite deposits and evaporation of seawater.
Salt has many uses in cooking beyond simple flavoring. Its chief utility lies in its osmotic properties. Salting the surface of food draws out water and anything dissolved in it. When meat is koshered, it is heavily salted to draw out any remaining blood. Kosher salt, because of its structure, is perfectly suited to this task. This technique is also applied to eggplant to remove bitter flavors and alter the texture of the plant, and also when sweating aromatic ingredients such as onion or garlic over low heat to draw out their moistures and soften them.
Salt is frequently used in fermented foods, both for drawing the liquids out of vegetables and to inhibit the activity of undesirable bacteria. It is generally recommended that non-iodised salt be used for fermenting, because iodine is an effective antibacterial substance and can thus inhibit the fermentation a little. Iodised salt will work in a ferment, but it is better to use a non-iodised salt like pickling salt or kosher salt.
Salt also tends to enhance our perception of other flavors, particularly that of sweetness. This explains its use in ice cream, for example, or kettle corn. Most candy recipes have a small amount of salt which cannot be directly detected, but has a noticeable effect on the final result. This is because salt lands on the taste buds and sort of opens them up for other flavors
Salt's thermal properties are useful in a few applications, notably in home-made ice cream. The action of rock salt dissolving in ice water makes a solution colder than ice itself.. Ice cream makers, then, sit the salt-and-ice mixture in an insulated container, and inside that is placed a highly conductive container of the cream mixture, which freezes rapidly.
Salt can be used to "fry" food as well. Large amounts of rock salt are heated in an oven to temperature (varies, generally about 400°F or 200°C). After the salt gets hot, the food is placed in the salt and an additional layer of pre-heated salt is poured on top. This method is an extremely fast way to get heat into food, second only to deep frying, consequently, cooking times will be very short.
When salt is added to boiling water for pasta or potatoes, the temperature of the water can rise by a very slight amount (less than a degree). The main effect is flavoring. However, you are salting the water, not directly salting the food. Thus the amount of salt should vary according to the amount of water; quite a bit is usually required.
Lastly, salt is of course used as a direct flavoring. Ordinary table salt is most often used for this purpose; it brings out the taste of the other ingredients and has added iodine which prevents goiter. Many gourmets, however, prefer uniodized coarse salt because they have a sort of "cleaner" taste. Sea salt also has a potential to have health benefits that other salts lack because of the minerals and whatnot in the ocean.