: You cannot open part1 successfully unless you have all subsequent parts (e.g., part2 , part3 ) in the same folder.
To access the original content, you must treat these separate parts as a single entity.
: The file extension .rar identifies it as a Roshal Archive , a compressed format developed by Eugene Roshal. How to Extract and Combine the Parts
A file ending in .part1.rar is part of a "split" or "multi-volume" archive.