Generic filenames like "File020.rar" are frequently used by to hide the true nature of a file. If you received this file as an email attachment or downloaded it from an untrusted website: Do not open it without scanning it first.
Knowing the source (e.g., a specific website, an old hard drive, or an email) would help me give you more specific information. File020 rar
You might see files labeled File.part01.rar , File.part02.rar , etc. Generic filenames like "File020