Kosher salt is, well, kosher.
But, so is table salt.
Kosher salt is called kosher salt due to it's ability to draw blood to the surface of meats in a kosher way.
Kosher salt is also a larger, coarser grain than table salt.
It has no anti-caking additives or iodine added.
Kosher salt and table salt may be used in place of each other, but do not use equal amounts.
You would use more kosher in place of table salt.
If you are using table salt instead of kosher use less.
There is a slight difference in flavor.
Table salt is a bit sharper.
I like to cook with kosher salt.
It just brings a different depth to the dish.
Many of the seasoning rubs I make have kosher salt in them.
A couple that I have on this site are creole rub and sazon.
Kosher salt may or may not be sea salt.
Sea salt comes strictly for evaporated sea water.
Kosher salt may come from evaporated sea water or it may come from salt mines.