Sodium chloride is formed from hydrochloric acid and sodium hydroxide. Hydrochloric acid is the acid and sodium hydroxide is the base. It is a neutral salt because it is formed from a strong acid and a strong base.
Sodium chloride is called rock salt when it is found in the earth in the form of large crystals. Rock salt is usually brown or pink due to the presence of impurities.
Rock salt is formed when sea water or salt lakes dry up over a long period of time. As the water evaporates, the salt is left behind. It gets deposited in layers and becomes buried under the ground. These deposits of salt are called rock salt and are mined from the earth.