Ayers Rock, also known as Uluru, is a sacred rock to the aboriginals (native people). As it is 348m (1,143ft) high, it is considered the largest solitary (single or existing alone) rock on the planet. Its red sandstone surface has been smoothed by high winds over time.
The image above is of Uluru.
Red sand dunes are scattered all over the Great Sandy Desert. They are also formed by high winds. The bases are more or less solid from being in the same position for hundreds of years, however the tops are loose and drift with the wind.
The image above is a red sand dune in the Great Sandy Desert.