A file named is a specific type of compressed data known as a split archive part . The ".001" suffix indicates it is the first segment of a larger file that has been divided into multiple volumes for easier sharing or storage. Understanding the .7z.001 Format
The format is an open-source archive type created by the 7-Zip software . It is widely used because it offers a high compression ratio and supports advanced features like AES-256 encryption . How to Extract .7z.001 files - Microsoft Q&A chibip.7z.001