This indicates the original, uncompressed, or master file uploaded to a server. Most platforms (like YouTube or Vimeo) take this "source" file and create multiple smaller versions (transcodes) at different resolutions (360p, 720p, 1080p) for users to stream.
This alphanumeric string is likely a hash or Unique Universal Identifier . It is used by databases to track a specific file without relying on human-readable names, which could be duplicated. 0gxvoihlsjhjlgr7da1uu_source.mp4
If the file is too large (common for "source" files), it can be converted to smaller MP4 variants for easier sharing. This indicates the original, uncompressed, or master file
Files designated as "source" MP4s are built for high-fidelity storage before they are processed for the web: This indicates the original