Sourdough is a type of bread made through a natural fermentation process using wild yeast and lactic acid bacteria. Unlike breads made with commercial yeast, sourdough relies on a starter—a mixture of flour and water that captures microorganisms from the environment. This slow fermentation gives sourdough its distinctive tangy flavor, chewy texture, and crisp crust. It’s known for being more digestible and having a longer shelf life than conventional breads, and is enjoyed worldwide in a variety of styles and recipes.