The "part12" suffix follows the best practice of using leading zeroes or numbered suffixes to ensure the archive segments remain in chronological or logical order during processing.
The .rar extension indicates a compressed format. As part 12 , it is a middle segment of a larger set; you cannot open or view the contents of this specific file without having all other parts in the sequence. General Write-Up & Identification
When documenting or identifying files in an archive, standard file naming conventions prioritize descriptive, unique, and human-readable names .