dear bel-- in US, there are several salts-- salt for the street, is usually called "rock salt" but i like the name big salt..since rock salt is large (small pea --petit poi) sized crystals. it is almost never used for "consumption", but finds it way into "salt beds" for baking oysters, and in with the ice for making home made icecream. most commonly, it is used to melt ice on the street. Some of the new compounds, the are less caustic, and work at lower temputures, are simple referred to as "good" or the "the good stuff" rock salt, but these are not sodium chloride.

next down in size is Kosher salt, which is used for lots of things, ethnicaly, it is use by Jews in a koshering process, to remove all the blood from food, but it is also the salt used for salted pretzels, and other food. it is a very pure salt, and most pickles recipes call for kosher salt.

sea salt-- sold as a gourmet item, is the next size in salt. it is almost the same size as kosher salt, maybe a little finer, and is almost always served in a grinder, like a pepper grinder, to grind it to a finer consistanty. (and i confess, my personal preference)

finaly, table salt, both iodized, and plain. very fine crystals.