Kosher or sea salt is essential for building flavor while cooking, but when it comes to adding a final burst of flavor or crunch, finishing salts are handy to have around. They're typically flakier or denser than cooking salts for the very reason that you want them to create texture—a light dusting administered at the last minute can completely change the profile of your dish.
To add a final saline punch to roast chicken or vegetables, use that fine-grained, classic version harvested off the shores of Brittany known as fleur de sel. Smoked salts, which are typically infused over hickory, applewood or alderwood, add an elemental taste of the fire (use them sparingly—too much and your dish can taste like liquid smoke). Hawaiian sea salts, particularly the pink variety, have a mellow flavor that's suited to pork or beef. With heartier meats like lamb we sometimes reach for fragrant, herbaceous lavender salt.
It's great to have a few different finishing salts on hand to tailor to the texture and flavor of whatever your cooking, but when in doubt, the delicate little pyramids of Maldon salt are always a happy sight.