Rye bread and sourdough are both types of bread, but they are not the same. Rye bread is a kind of bread produced from rye flour, while sourdough is a type of bread made from a sourdough starter. A sourdough starter is a yeast-fermented mixture of flour and water. Sourdough bread has a sour taste and a chewy texture. Rye bread has nutty and earthy flavors and a dense texture.