Coarse pickling salt and kosher salt are very similar. Both are large-grained, coarse salts which contain little to no additives. Kosher salt is made without additives because of Jewish dietary laws and is used in kosher butchering. Coarse pickling salt is made without additives because these can cause pickles to discolor and brine to become cloudy. Below are a few more details you might want to know for any and all of your pickling needs.
Kosher salt grains have a large surface area. It is very flaky and adheres easily to food surfaces, while coarse pickling salts only real difference from kosher salt is that some brands of kosher salt contain anti-caking additives, while coarse pickling salt never contains these.
In addition to being used in butchering, kosher salt may also be used to make brines, compose salt crusts for meats and line mixed drink glasses (such as margaritas and Bloody Marys.) It may also be used as table salt. Coarse pickling salt is usually used exclusively for pickling.
Kosher salt and coarse pickling salt can be substituted for each other in some applications. However, kosher salt is not an optimal substitute for coarse pickling salt in pickling because it may contain anti-caking agents and it measures differently than coarse pickling salt, which may throw off recipes.
Unlike other types of salt, both coarse pickling salt and kosher salt are not iodized.
Neither kosher salt nor coarse pickling salt should be substituted for table salt in baking.