What makes kosher salt kosher?
Kosher salt is not kosher in and of itself. Kosher rules prohibit consuming blood, so it is better thought of as "Koshering Salt" since its purpose is to draw fluid out of meat, making it kosher. Its large crystals make it useful in cooking, and "kosher salt" is easier to work with than table salt.
kosher salt and sea salt are the same. Kosher salt earned its name from it's original purpose to kosher meat meaning to bleed out the blood from the animal. It has nothing to do with kosher dietary guidelines. Sea salt is directly evaporated from seawater.