If you are trying to manage or use this specific archive, here is what that file represents:
: Large games are often split into smaller pieces (like .part01, .part02, etc.) to make downloading easier. Part 20 is just one segment of the total data.
: If you only have part 20, it is unusable on its own. You would need the preceding 19 parts and any subsequent parts to extract the content.
: To use this, you must have all parts (part01 through the final part) in the same folder. Opening any single part (usually part01) with a tool like WinRAR or 7-Zip will automatically pull data from the rest to reconstruct the full installer.