Honey Block

Honey blocks are sticky blocks craftable from honey bottles.

Obtaining
Honey blocks can be broken instantly, regardless of held items.

Usage
Mobs avoid walking on honey blocks.

Unlike the slime block, the honey block does not carry a redstone signal.

Pistons
When pushed by a piston, entities on its top surface and adjacent blocks move with it. Mobs are not launched high in the air if a piston pushes them up, unlike the slime block's behavior. As of 19w42a, honey blocks and slime blocks do not stick together.

Slowing down entities
Honey blocks slow down entities walking on top of them and prevent them from jumping. Players, who can ordinarily jump about $1 1/4$ blocks high, can only jump about $3/16$ blocks high on honey; this is an 85% reduction. They can more easily step up onto other blocks than jump up onto them.

Sliding


Entities attaching to the sides of a honey block slide down at a slow speed and do not take fall damage, similar to going down a ladder but with a gradually decreasing horizontal momentum. This allows players to jump 2 blocks further by holding on to the walls.

Falling
As with hay bales, falling onto a honey block reduces the fall damage by 80%, for example, if a player or mob falls from a height and would otherwise take of damage, then if they land on a honey block they actually take  damage.

Bees
When a honey block is near bees and a beehive or bee nest, bees will occasionally fly close and attach to it for a few seconds, resembling an action of "eating honey". When doing this, the bee stops fluttering its wings, and firmly attaches its face to the honey block. This is regardless of whether any flowers are around.

Trivia

 * Honey blocks are not full blocks: despite taking up 16 pixels, the collision box is only 14  pixels.
 * Small entities such as arrows are free to move through the gap between honey blocks as they are under 2 pixels wide.
 * Only when entities are partially "in" the honey block (i.e., they are touching the 14 -pixel hitbox) can they slide down against it.
 * In real life, bees eat honey when the temperature is low and flowers are difficult to find. Otherwise, pollen is their primary food.
 * Honey blocks will slow down players regardless of their movement (flying with elytra, swimming, etc).
 * The bottom surface of the honey block does not slow down entities.