As mentioned, a .001 file is useless without its partner pieces. You cannot simply rename it to .avi and expect it to play correctly.
To view the content of an .avi.001 file, a user typically needs all subsequent parts (the .002, .003, etc.). Once all parts are downloaded into the same folder, a file joiner utility merges them back into a single, playable .avi video file. Cultural Significance
Filenames like this serve as "digital artifacts." They represent a specific time in internet history when metadata was manually entered by uploaders and file naming conventions were strictly followed to help users navigate massive databases of imported media.