Splitting files is used to overcome file size limits on file-hosting sites, speed up downloads (by allowing parallel downloads), or make it easier to transfer large amounts of data, such as high-definition videos, software packages, or backups [2].
If you attempt to extract the files and receive a "CRC error" or "unexpected end of archive," it usually means one of the parts (like part3 ) is corrupted or missing [1]. To help you further with this file, I need to know: Did you download this yourself , or did you receive it? 0001-0020.part3.rar
Are you getting a specific when trying to open it? Do you have all 20 parts downloaded? Splitting files is used to overcome file size