Sand is a common physics obeying block that can be found in deserts or next to water. Being a "physics obeying block" means that it will turn into a falling block entity and fall down until it hits a solid block, and turns back into a normal Sand block, or hits a non-solid block and turns into an item. 4 Sand can be crafted into one Sandstone by placing it in a square, or crafted into TNT by combining it with Gunpowder in a checkerboard pattern, and can also be smelted into Glass.
In chunks generated after Beta 1.2's release, the bottom of all Sand piles had a layer of Sandstone.
Before Beta 1.8, the spawn point of a world when created would always be on Sand.
In the PC and Pocket Edition, particles are released by unstable sand.