Here's a link to a beautiful write up. One I refer to often, it explains the different types, and the reasons why we MUST consume salt. It is inspiring. One of the reasons I add a pinch of Celtic Sea Salt to my drinking water.
ps: As for the regular salt, it is very useful to:
*Scrub pots: sprinkle in and rub vigorously with a paper towel.
*Control smoke: when something spills over in the oven and starts smoking, sprinkle salt generously on the spill and it will stop the smoke until you are done cooking and can take care of cleaning it out.
*cook fish: fill a (low) bakeware with salt place in oven to heat - place fish or seaffod (with the skin or shell side down) and place in the oven to cook. When done remove the skin or shell and discard.
*Sprinkle in the driveway to melt snow or add traction to a walkway.
*Emollient: Add olive or castor oil and rub cracked / dry feet.
*Control grease fire: if grease creates a fire on your stove or grill sprinkle generously with salt, it will choke the fire, and keep it out while you finish grilling.
Hmmm.... There may be more I believe it can also be used to bleach whites. But don't know the process (I think boil salt water, remove from fire and soak item)