Actually it comes from the rocks that erode into the seas located around the globe. From Utah, to the Pacific ocean, to France and the Himalayans salt is harvested world wide. In its pure form salt in known as sodium chloride. It has been harvested by every known community. And up until the 19-20th centuries it was used primarily as a preservative to keep meats and other foods from spoiling and as a flavor enhancer.
Interestingly enough with the onset of the industrial revolution salt came along for the ride. It is used in something as simple as salting a road or a sidewalk to prevent water from freezing into ice. It is used in water treatment facilities to soften water. Salt is now "manufactured" worldwide, depending on its location it can be highly processed or simply air dried to ensure purity and quality.
Because salt is a naturally occurring product it carries with it minerals and trace elements that can add undesirable flavors. These minerals can be "washed out" of the salt by a brining method to remove the offending "bitter" elements. A couple of the biggest offenders are magnesium and calcium. Large salt manufacturers remove these to give table salt the recognizable nice white clean look and taste is has today. Interestingly enough though I notice that they add in calcium silicate and magnesium oxide to prevent clumping. ??? Odd they remove these minerals as undesirable flavor elements and add small amount of derivative elements back in to make them easier to deal with in mass production quantities. When the anti-clumping additives are added they are usually in small amounts of less than 2% of the whole batch.
The picture shows an assortment of salts in my cupboard. Let's discuss them individually.
1. This is good old iodized table salt. Morton's to be exact. It is probably on just about every table in America. In the 1920's manufacturers began adding potassium iodide to salt to prevent iodide deficiencies in humans. One note - if you live in area where they chlorinate your water - dissolve some in water. Let it sit for a bit. What do you smell? Some people can smell seaweed. If you don't know what seaweed smells like, you'd never figure it out. The smell is created when the chlorine in the water mixes with the iodide. Weird? Not really. Quite salty, and it has a underlying aftertaste. Maybe the iodides.
2. Hain's non-iodized pure sea salt. This is Hain's version of kiln dried and processed sea salt. It is purified to remove bitter minerals, then they add Calcium Silicate to prevent clumping. Taste? Pretty much the same as Morton's, not a noticeable aftertaste.
3. Kosher Salt. Kosher salt is never iodized. It comes in large crystals and flakes. It is lighter in flavor and is a favorite of cooks countrywide. When you look at the picture, closely, in the foreground are a couple of triangular shaped pieces. This is natural phenomenon of salt crystals when the evaporation process is done slowly, thus allowing the crystals to form larger and triangular in shape. Kosher salt must be used when preparing meats according to Jewish dietary laws. It is salty, you can use less because of the larger crystals. I use it in meat preparation and with sauces
4. Fleur de Sel (fine). This is the La Baleine brand from the coast of the Mediterranean. I was surprised to find this wonderfully flavored salt quite inexpensive. Yes it was still triple the cost of regular Morton's however it was not cost prohibitive. This salt is harvested directly from the coast line and then rinsed in the "clear blue waters of the Mediterranean". This is my favorite salt. I use it in all of my cooking. The flavor is salty, and i can't describe it in words other than to say it has a "clean" - possibly pure flavor. 
5. Himalayan. This example of salt without minerals and elements removed. It is harvested at the foot of the Himalyan mountains. Himalayan salt has a definite pink hue. The hue comes from minerals such as calcium, potassium, sulphur, magnesium, iron, copper and zinc. Most of these are only present in trace amounts, yet enough to alter coloration. Producers note that this is how salt was meant be savored. Most refer to it as unrefined salt, meaning "processed without removal of any minerals. However, these minerals add thier own disctinct flavors. Some people find them bitter. It does have a bit of an aftertaste. Used correctly, it should still give good results in certain preparations. 
6. Real Salt. Redmond Utah. This is much like the Himalayan salt. It is quite fine and has less of an aftertaste than the Himalayan. It does share its pretty pink hue though. looking closely you can see the bits and pieces of other elements. Real Salt was awarded the 2004 Best taste award from the American Culinary Society. It is a nice table salt and used sparingly should be enjoyed by all. 
7. Solar Sea Salt. This is harvested off the coast of the pacific ocean. Solar sea salt is allowed to dry a bit then is rinsed clear in sea water then placed ina kiln to finish the drying process. The size of the crystal indicate it is slow evaporated prior to final kiln drying method. I use this salt when preserving herbs, citrus or the occasional salmon filet. There are other salts available. Colored and flavored varieties such as celery salt and garlic salt. There are also smoked salts available in Wales, Denmark and India. The black salt of India is much like the Real Salt of Utah, it has minerals which give it color and flavor. There is also a famous "sel gris" - grey salt. Sel gris is an unrefined form of salt still containing magnesium and other elements which gives it a distinctive coloration. On the horizon: Pastry chefs have begun developing "sweet" salts for use with pastries and confections. In my latest Pastry Art & Design (March 2005) magazine an article shows us how to make a fruit salts. Chef Cory Colton is using fruit infused salts to add taste and texture.
The sky's the limit! Try something new with salt in your kitchen - you may surprise yourself how this simple seasoning can become a star in your preparation.
Please don't use my taste example as yours. Taste is in the tongue. We all have different receptors in our tongue making the taste of something very personal. Try a few of these salts, choose one that meets your needs (and the needs of the recipe) and likes. Don't use something because everyone else is using it.
