Snow Block

A snow block is a full-sized block of snow.

Obtaining
When broken with a shovel, snow drops snowballs. If mined with a Silk Touch enchanted shovel, it drops a snow block.

Unlike snow layers, snow blocks will not melt from higher levels of light under normal circumstances, nor get destroyed by water.

Natural generation
Snow generates naturally in ice plains spikes biomes, in igloos and in any "cold" biome when it rains (snows).

Snow Golems
Snow is also used to make snow golems by putting 2 snow blocks on top of another and a pumpkin on the top as the head. Note that the pumpkin has to be placed last for this to work. This can be done sideways and upside-down, as well. Snow golem fact - Shearing it using shears the pumpkin will come off and show a rather derpy looking face!

Trivia

 * Snow may still fall on top of snow blocks, making them look taller than they actually are.
 * When a snow block is on grass, the grass block changes to a different "snowy" texture as if a snow layer is on it.
 * However, since snow is not transparent to light, the grass will change to dirt shortly after.
 * There is code to make snow blocks melt, but since they are solid blocks they cannot be lit enough for this to occur (barring certain lighting glitches) (see for more information)
 * A texture known as "fluff.png" exists in files from the survival tests onward, that resembles snow. However, this was before snow was added, so this texture went unused.