Multi-part file downloads, indicated by extensions like .part1 or .001, involve breaking large files into segments that require all parts to be present in the same folder for successful extraction. Using software such as 7-Zip or WinRAR, opening the first segment allows for the automatic reassembly of the original file. When downloading from file-sharing sites, it is critical to verify file extensions to avoid malware, utilize ad-blockers, and ensure sufficient disk space for both the compressed parts and the final extracted file.