A single large file that has been split into several pieces. Part 2 is the second segment of that original file.
The file refers to a specific volume of a multi-part compressed archive. In computing, large archives are often split into smaller "parts" (like Part 1, Part 2, etc.) to make them easier to upload, download, or store. Understanding Multi-Part RAR Files DiBrKa Part2 rar
To successfully extract the content, you must have all parts (Part 1, Part 2, etc.) in the same folder. A single large file that has been split into several pieces