1. The Definitions
* Data Loading: Importing values into blocks.
* Physical Clear: Wiping data and shrinking the database size on disk.
* Logical Clear: Marking data as #Missing; faster but doesn't immediately reclaim space.
2. The Whiteboard Analogy
* Data Loading: Writing problems on the board.
* Data Clearing: The eraser. If you don't erase properly, old numbers mix with new ones and create errors.