A sourdough starter is a fermented dough made from flour and water. It is used to leaven bread, giving it a characteristic sour flavor. Sourdough starters are made by combining flour and water and allowing it to ferment for several days. During this time, wild yeast and bacteria grow in the starter, which produce the sour flavor.
Sourdough starters have been used for centuries to make bread. They are said to have originated in ancient Egypt, where they were used to make a type of flatbread called pita. Sourdough starters are also popular in Europe, where they are used to make a variety of breads, including sourdough rye bread and sourdough baguettes.