A file ending in .part1.rar is part of a "split" or "multi-volume" archive.
: Large files (often >4GB) are broken down into smaller chunks (e.g., part1.rar , part2.rar , etc.) to stay within file size limits of hosting sites or to speed up individual downloads.
: Once all parts are present, right-click only the file ending in .part1.rar . Most modern decompression tools like WinRAR or 7-Zip will automatically find and join the other parts to extract the full original file.