Apps often rename files when saving them to your local device storage to prevent naming conflicts.

A very small file (KB) is likely a short clip or meme; a large file (MB/GB) is likely a full video or high-definition recording.

Many NVR (Network Video Recorder) systems use numerical strings to timestamp or index clips.

If you have the file and are trying to figure out what it is without opening it, you can:

Large repositories or "leak" sites often use numerical IDs to catalog content anonymously. How to Identify the File