David's Kosher Salt are large, rough crystals that take a long time to dissolve.
Kosher salt is often recommended by chefs as it has a less intense and more pure, salty taste and because it's easier to pick up the crystals and toss them into the pot, meaning that you avoid putting too much (or not enough) salt in a dish.
Perfect for cooking steak and drawing the flavour out of vegetables when blanching.