A dune is a mound of sand formed by the wind, usually along the beach or in a desert. Dunes form when wind blows sand into a sheltered area behind an obstacle(Obstacle may may a rock, tree or trees stump etc). Dunes grow as grains of sand accumulate. Every dune has a windward side and a slip-face. They are form in areas of with less obstacle that’s is desert areas and beaches. They are maybe of different shape depending on the intensity of the blowing wind, the direction along which the wind blows and that amount of sand the obstacle is able to stop.