At some point you’ve probably plugged in a USB flash drive and thought, “Why are there two drives showing up?” Or maybe Windows refused to delete a mysterious read-only volume. Or Disk Management showed something you couldn’t remove no matter how many times you formatted. These moments usually lead to confusion, frustration, and a lot of bad advice online.

The issue almost always comes down to misunderstanding two concepts that sound similar but live in very different layers of storage behavior: Logical Unit Numbers (LUNs) and partitions. Once you understand the difference, a lot of strange USB behavior suddenly makes sense.