: In professional video editing, files are often labeled by project codes. "PM" might stand for Project Manager , Product Marketing , or a specific internal project code (e.g., "Project Midnight").

Provide more context so I can help you find the exact content. changing meta data for mp4 files - Microsoft Community

: It likely uses the H.264 (AVC) or H.265 (HEVC) video codec.

: Right-click the file and select Properties > Details (Windows) or Get Info (macOS) to see the date it was created, which may provide a clue to its origin.