The .001 suffix identifies this specific file as the "head" or index of the archive. It contains the metadata required for an extraction tool to recognize the sequence and begin reassembling the original content. The 7z Format
Meet file size limits for email attachments or cloud storage. Fit large data sets onto portable storage media. bwolfb.7z.001
A .7z.001 extension indicates that a larger original file was "spanned" or split into smaller pieces to facilitate easier distribution. This is often done to: bwolfb.7z.001