The .001 file acts as the "index" or entry point. Archiving software uses this file to identify the set and begin the reconstruction of the original data.
Split archives use progressive numbering (e.g., .001 , .002 , .003 ) to indicate their order. 01t.7z.001
The file extension identifies the first volume of a multi-part 7-Zip archive . This format is typically used to split a single large archive into smaller, more manageable segments for easier storage or distribution. Technical Overview 01t.7z.001