difference in files (Killers, LOL, 2HD, Evolve, etc.)

[BoviemuffGuest]

Sometimes I see the same video, even by the same uploader but with different 'extensions' in the file name. Most common are Evolve, 2HD, Killers , FUM.

I curious as to the difference in the files aside from the file size.

[imPROvise]

(Killers, LOL, 2HD, Evolve, etc.) - Those are group or person names that did the encoding of the video and is used to give credit to that person or group.