A finishing salt is a salt used almost like a spice just before serving the food. Its flavor and texture should complement the dish. Many regular salts have anti caking agents and they taste bitter. A finishing salt is usually artisan and differ in taste, texture, humidity/water content/ and mineral content depending on how and where it was obtained. A common example (in my home) is flake salt from Maldon sprinkled on your vegetables in a salad just before adding olive oil and vinegar (in that order, although I am sure there will be disagreement with this), or fleur de salt over pork or beef, shio salt on top of fish or pink Himalayan salt hand grated (which by the way, does not come from the sea but from mines, and it does not come from the Himalayas but from Pakistan but is marketed that way not to offend some sensibilities) on top of sauce much like pepper, coarse Mediterranean salt on top of a porterhouse... it is fun to get a few distinct salts and conduct a "tasting"... by the way, I am not including flavored salts here, where the salt is mixed with other things for flavor, such as saffron, piment d'espelette, etc.
