Salt is a staple in the diets and food cultures of all people. Human physiology requires salt. Salt brings out flavor. A quality cook understands the power of salt. Salt can make a dish the greatest thing you have ever tasted, or render the dish inedible garbage. Bread can be made without salt. Naan, India's flat bread, can be made with out salt, and other flat breads can be made without salt. Salt enhances the flavor and slows down the fermentation process of bread. Longer fermentation time allows the ingredients--the flour, sourdough starter, nuts, olives, seeds, oils, molasses, kale, bacon,--time to fully integrate, flavor to reach a full complexity, and the gluten to strengthen. Salts are not all the same. Some bakers do not use iodized salts, because they impart an iodine flavor, some only use a fine salt so it dissolves into the dough quicker. Use what is available to you. I use coarse sea salt, add it to some hot water and let it dissolve while the water cools.