** Idli-dosa batter is a fermented mix of rice, urad dal, and fenugreek, known for its versatility to make fluffy idlis (thicker batter, coarser grind) and crispy dosas (thinner, finer grind), offering protein, carbs, and probiotics, requiring minimal prep when bought ready-to-use, and relying on natural fermentation for flavor and lightness. Key features include its tangy taste, airy texture after fermenting, nutritional value, and gluten-free nature, making it a staple in South Indian cuisine.