Dried herbs are fresh aromatic leaves with their moisture removed, which concentrates their essential oils into a more potent, shelf-stable seasoning than the fresh form.
Common examples include basil, oregano, thyme, rosemary, sage, marjoram, parsley, and bay leaves. They are used whole, crushed, or ground to season meats, vegetables, sauces, and soups, and are especially common in Mediterranean, Middle Eastern, and European cooking.
Because drying concentrates flavor, dried herbs are more potent than fresh: a common substitution rule is to use about one-third the amount of dried herb called for in fresh form. Flavor fades over time, so buy in small quantities and store in an airtight container away from heat, light, and moisture.
Herb blends such as Italian seasoning, herbes de Provence, and za'atar combine several dried herbs and spices into a single seasoning mix used as a rub or marinade base.