Salt, also known as table salt, or rock salt

Halite  commonly known as rock salt, is the mineral form of sodium chloride (NaCl).
The mineral is typically color.
Halite occurs in vast beds of sedimentary evaporite minerals that result from the drying up of enclosed lakes, playas, and seas. Salt beds may be hundreds of meters thick and underlie broad areas.
Salt domes are vertical diapirs or pipe-like masses of salt that have been essentially "squeezed up" from underlying salt beds.
Salt, also known as table salt, or rock salt, is a mineral that is composed primarily of sodium chloride (NaCl). Table salt is largely rock salt that has been crushed and purified.
Halite is often used both residentially and municipally for managing ice.
Salt is also used extensively in cooking as a flavor enhancer and to cure a wide variety of foods such as bacon and fish. Salt is one of the oldest, most ubiquitous food seasonings and salting is an important method of food preservation. The taste of salt (saltiness) is one of the basic human tastes.
Salt is also used in the production of ice cream. It is not actually used in the ice cream mixture; rather, it is used to melt the ice surrounding the can holding the ice cream.
While people have used canning and artificial refrigeration to preserve food for the last hundred years or so, salt has been the best-known food preservative, especially for meat, for many thousands of years.
Salt was included among funereal offerings found in ancient Egyptian tombs from the third millennium BC. The harvest of salt from the surface of Xiechi Lake near Yuncheng in Shanxi, China dates back to at least 6000 BC.
Mahatma Gandhi led at least 100,000 people on the "Dandi March" or "Salt Satyagraha", in which protesters made their own salt from the sea, which was illegal under British rule, as it avoided paying the "salt tax".
Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. The completely raw sea salt is bitter because of magnesium and calcium compounds, and thus is rarely eaten.
Unrefined sea salts are also commonly used as ingredients in bathing additives and cosmetic products.
After the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. Purification usually involves recrystallization. Table salt is refined salt, which contains about 97% to 99% sodium chloride.
Iodine-containing compounds are added to table salt. Iodine deficiency affects about two billion people and is the leading preventable cause of mental retardation.  The practice began in 1924.
Iodized salt is thus table salt mixed with a minute amount of potassium iodide, sodium iodide, or sodium iodate. Iodized salt is used to help reduce the incidence of iodine deficiency in humans.
Iodine deficiency commonly leads to thyroid gland problems, specifically endemic goiter, a disease characterized by a swelling of the thyroid gland.
In Western cuisines, salt is used in cooking, and also made available to diners in salt shakers on the table. So Table salt is refined salt. For 4,000 years, we have known that salt intakes can affect blood pressure through signals to the muscles of blood vessels trying to maintain blood pressure.
Many chefs prefer kosher salt in cooking certain dishes, usually as a topping, to add special crunch or taste to food. Kosher salt is made by similar evaporation processes as cubic table salt, both plain and iodized.  This condiment is used in India and is used extensively in Indian cuisine during fasting days.
Rock salt is used as a condiment or added to chaats, chutneys, raitas.
Store salt in an air tight container. Salt is salt. So long as it contains sodium (and all forms of table salt do), then it will raise your blood pressure and could damage your body. So people need to be careful when using  salt. 
Sea salt is evaporated sea water. All salts are nutritionally the same. Black salt named Kala Namak in India, is really a blend of minerals having  a strong sulfur odor.  It is commonly used in snack foods in North India. Kosher salt is an additive free coarsely grained salt.

Less intake of salt is good 4 health...
Almost all foods contain some sodium naturally. Dairy products, meats and fish are generally higher in natural sodium than fruits, vegetables and grains.
Most of the sodium we consume comes from the added salt. The salt we add in cooking and at the table, and salt that is added to processed foods. Sodium also occurs in several commonly used food ingredients, such as baking soda, baking powder and soya sauce, as well as in many food additives and preservatives such as sodium nitrate.
To reduce amount of sodium in your diet:
Follow these simple guidelines:
1. Remove the salt shaker from the table:
2 Go easy on spices and condiments:
To increase food taste try adding new flavors like lemon|lime juice, onion, garlic, green chilies, pepper, vinegar or even a pinch of sugar| honey|jaggery
(if you are not diabetic).
3 Use less of canned or processed foods.
4 Less of fast foods.
5 Eat less of non vegetarian food also.