A file named part1.rar cannot be opened or used on its own. It is the first link in a chain. To access the actual content (likely a movie or a high-quality recording of a performance by the band Pantera), you generally need:
Sites like Mega or MediaFire, which often have file size limits per upload, necessitating the "part" system. P4NT3R4HD.part1.rar
This is the file extension for a WinRAR compressed archive. How Split RAR Archives Work A file named part1