The Peaceful Table is a block added by Extra Utilities. It allows players in Peaceful Mode to collect mob drops. For it to work, it needs to be placed next to a block with an inventory, and the inventory needs to have a sword. This block also only works in Peaceful Mode.
The block will occasionally spawn a mob on top of itself and instantly kill it. The amount of durability the sword loses is dependent on how many hits it would take to kill the mob. It will also take enchantments into account (Sharpness, Unbreaking, etc.).