Salt was once a form of payment to Roman troops, that's how important it is to our health. Salt allows the tiny electrical signals in your brain and nervous system to be transmitted from one nerve cell to another. Salt helps your body to store water, necessary when doing strenuous labor. And that stored water helps to flush out toxins and other waste products, as well as cool your body via sweating - which is why sweat tastes salty.
Humans need roughly 25 lbs of salt a year. Most of this we get from our (overly) processed foods, and a lot is consumed by generous use of a salt shaker.
Table salt, the most common form, contains Iodine, a necessary vitamin that promotes Thyroid Gland health. Too little Iodine and you have problems.
Some folks need to limit their salt intake, too much and their blood pressure skyrockets. For them, there's Lite Salt. It contains less sodium and more potassium cloride (to achieve that "salt" flavor). Also included is some magnesium, and both chemicals are actually good for you.
Lastly, there's plain salt. No iodine included. This is also known as Kosher salt (which sells for quite a premium over non-iodized or plain salt) and is chemically exactly the same.
For you canners out there, you should not use Iodized salt in your canning recipes - Iodine will rot the inside of the canning lid causing premature loss of seal, as well as fouling the taste of the canned product.
Canning salt = Kosher salt = Non-Iodized or plain salt. Buy the cheapest one, it's all the same stuff!
So, to sum it all up, use Table salt (Iodized salt) at the dinner table, unless you have an issue with salt, then use Lite Salt. For canning, use non-iodized / Kosher / canning salt.
Oh, and you can use the Pink salt, Sea Salt, and all the other "gourmet" salts to impress your dinner guests!