You cannot open this file alone; attempting to extract it without the other parts will result in an error.
The .rar extension indicates a compressed archive file.
Exercise extreme caution if you downloaded this file from an unverified source, as compressed archives are frequently used to distribute malware.
The .part04 signifies this is the fourth part of a split archive . You need all preceding and subsequent parts (part01, part02, etc.) in the same folder to extract the contents.