Based on the components of your query, here is how those terms typically relate to the game's mechanics: Building and "Pieces"
The phrase does not appear to refer to a single known fact, official game item, or established community term within the survival game Grounded . grounded.rar
If you are looking for a specific "proper" piece of data or a rare item often sought after in community guides: Based on the components of your query, here
: Many specialized cosmetic and functional build pieces are locked behind the Coziness mechanic. To unlock them, you must place furniture and decorations to increase your base's "Max Cozy" level. official game item
: The Ash Wall is currently the sturdiest building piece available, crafted using Ash Cement.