They were introduced with update R26, the "Holiday Surprise" event.
The snowcube may be used quite similarly to a Force Bomb, albeit a lot cheaper and weaker. If timed correctly, you can throw one at the ground whilst falling and stop your fall, or "rocket jump" to increase velocity and air time.
From update R44 to update R50, these snowcubes did not hurt or kill Creatures nor player characters.
Since R50, snowcubes once again can be used to kill Creatures and also player characters.
Snowcubes cannot be placed into the game world, but they can be put on display on Stone Wall Shelves, on Placemats, Galactic Grav-Chambers, Frozen Containers, Snow Buried Containers and Hidden Temple Altars. They cannot be placed into Flower Pots nor Wood Planters.