Sweet potato starch is starch extracted from the sweet potato root and ground into a fine white powder that swells and thickens when heated with liquid, giving a smooth, silky texture. It's used as a thickener in East Asian sauces, gravies, and fillings, and, because it forms a stretchy, chewy gel, it's a key binder in foods like mochi, tapioca-style pearls, and glass noodles. It's gluten-free and often used in place of cornstarch or potato starch, though it isn't a direct 1:1 swap; recipes may need adjusted liquid and cooking time when substituting between them.