What is the difference between all-purpose flour and maida?

All-purpose flour and maida are both types of wheat flour, but they have different levels of refinement. All-purpose flour is a blend of hard and soft wheat, while maida is made from only soft wheat. All-purpose flour has a higher protein content and is suitable for a variety of baking purposes, while maida is finer and often used in Indian cuisine for making breads and pastries.