Sea salt is salt that is harvested from the evaporation of sea water (as opposed to mined salt). It can come in fine or coarse grains and hails from all around the world. France, England, Wales, Italy, Portugal, Hawaii, India, Mexico all harvest and market their own sea salts, which can come in a variety of colors, including black and pale orange. Most sea salts are primarily "condiment" salts, best used as a seasoning or finishing touch just before serving. Their flavor nuances and distinct colors and textures are apt to be lost when added during the cooking process; plus, they're expensive to pour into the pasta pot.
Recipes that call for “flaky sea salt, such as Maldon” are referring to a specific type of sea salt. Produced in the town of Maldon, Essex, England, where traditional salt-making techniques date back almost two thousand years, it’s different from other sea salts. To make Maldon salt, sea water is purified and then boiled to saturation, rather than sun dried, to create delicate, pure white pyramid-shaped crystals that crumble easily in your fingers and melt on your tongue. It’s a beautiful finishing salt for meats, breads, and other dishes. Less bitter than fine-grained salt, it pairs nicely with desserts as well.
Keep sea salt dry and it should last indefinitely. Keep it handy to sprinkle on foods as a finishing touch.