The .001 suffix means the original data was too large for a single file and was sliced into smaller, manageable chunks for easier uploading or storage.
The software will automatically detect the other parts and stitch them back together into the original file(s). Common Use Cases
Often denotes a "small," "sample," or "sub-split" version of a larger set. 7z.001: Standard 7-Zip split-file format. Technical Analysis