Large files are split to bypass the upload limits of hosting services or to fit onto smaller storage media like FAT32 drives.
If a single 50GB download fails at 90%, the entire file is lost. Splitting it into 5GB parts allows a user to only re-download the specific corrupted segment.
A file ending in .part3.rar is the third volume of a split archive created by programs like or 7-Zip . This technique is used for several reasons: