How it works
A partition defines a region of a storage disk according to its partition layout. A usable volume often includes a filesystem and may receive a drive letter, but those are separate layers. Several partitions on one physical disk do not create several independent hardware devices. If that disk fails, all of its partitions can be affected. Dividing files between them is therefore not a substitute for a backup elsewhere.
Operating-system installations can contain small boot, recovery or system partitions as well as the visible data volume. Removing an unfamiliar small partition to gain space can make startup or recovery fail. Free space inside a filesystem also differs from unallocated space outside partitions. Extending or shrinking requires a supported arrangement and can be limited by layout or files that cannot be moved during that operation.
Practical checks
Inspect the full disk map and identify each partition's purpose before changing anything. Preserve a verified backup and recovery information. Use the supported storage tools and read the effect of the selected action, particularly deletion, conversion and formatting. Do not assume a hidden partition is unused. After a planned change, confirm file access, booting and recovery as relevant. For a disk with missing files or read errors, prioritise preservation instead of experimenting with its layout.