Sand

The sand is a Gravity block as Gravel.

Breaking
Sand can be broken without tools, but a shovel is the fastest method of obtaining it.

Natural Generation
Sand generates naturally in many biomes of the Overworld near lakes or ponds, notably deserts, beaches, and rivers, generally in four-block-deep layers supported by stone and sandstone. Sand also generates as the ocean floor of lukewarm oceans, warm oceans, and their respective deep variants. It usually generates in quantities of 545 blocks per chunk on average in non-desert biomes.

Sand is also used to cover up buried treasure chests depending on where the chest generates in. (In this case, sand is used to cover up buried treasure chests that generate in beaches and ocean floors that are composed of sand, but in some cases stone or sandstone might be used instead).

Sand also generates as part of warm ocean ruins and some desert village houses.

Red sand generates naturally in badlands biomes and variants, always in a one-block-deep layer. Unlike sand, there is no red sandstone that supports it below.

Both types of sand can spawn floating in the air. The floating cluster of sand falls when one of the sand blocks receives an update (e.g. when a block is placed near it or when a block near it is broken).

Trading
Wandering traders sell 4 red sand for three emeralds.

Wandering traders also sell 8 sand for one emerald.

Usage
If the supporting block below a block of sand is removed, it falls until it lands on the next available block. More specifically, the sand block turns into a "falling block" entity, which is affected by gravity; when the falling block lands on a block with a solid top surface, it becomes a block again. More information about the falling block entity are available in the main article listed above.

If falling sand lands and covers the head of a mob or the player, the mob or player buried in it continuously receives suffocation damage. If falling sand lands in the space occupied by a non-solid block (such as torch, slab, rail, or redstone dust), it drops and turns into an item. If it falls onto a cobweb, it falls slowly until it has gone through completely; if it touches the ground while still inside the cobweb, it becomes an item. Sand that falls onto a lifting bubble column floats on top of the water until the bubble column is blocked or removed.

Though TNT does not break any blocks if explodes underwater, if sand, concrete powder, or gravel falls and covers the TNT before it explodes, blocks are broken as normal. This trick can be used to collect blocks underwater, or break into underwater structures such as the ocean monument without mining.

Construction
Sand can be used in the construction of airlocks and mob suffocation traps.

Farms
Sand or red sand is required for farming cactus, and can also be used for farming bamboo, sugar cane and kelp.

Note Blocks
Sand and red sand can be placed under note blocks to produce "snare drum" sound.

Trivia

 * If a block of sand has snow on it and is made to fall, the snow is destroyed‌[Java Edition only] and does not drop snowballs.
 * Since falling sand is considered an entity, it can be launched in a TNT cannon, similar to an ignited piece of TNT.
 * Sand falls at the same rate when submerged in water, or lava, or air.
 * If a player is standing on a stack of sand or gravel, and the stack falls onto a non-solid block, the player can fall fast enough to take damage or even die.
 * Sand falls through torches without breaking, if there is air below the torch.
 * Sand and gravel take about 0.45 seconds to fall one meter.
 * The sand texture is rotated if a block of sand turns into a  entity, similar to ignited TNT blocks. This is not the case with gravel.
 * Since  is considered an entity, blocks of sand without supports may disappear for a split second and a   entity is summoned. This is also the case when it's landing, but the entity (not the block) disappears instead before a block is placed.
 * Sand or gravel placed on top of a 2-block-high plant floats in the air until receiving a block update. This glitch was removed and later restored intentionally.