When breaking a block, for example dirt, the block "unbreaks" and returns to the original unbroken state when a collectible block around you goes into your inventory. For example, I'm breaking down a tree and I break one piece but after it breaks I then go on to break another piece for wood and I have already broken that piece halfway and then the block I broke earlier goes into my inventory, it resets the block I am currently breaking. When breaking the block I am using a tool, not bare hands.