What (software, document, media) do you expect it to be?
RAR files, particularly those found on unofficial, file-sharing, or torrent sites, often contain malware, viruses, or ransomware. JM–WeLitN rar
If this is a file you received, it is highly recommended to verify its source directly with the sender before interacting with it. If you can provide more context, such as: did you find this file (website, email)? What (software, document, media) do you expect it to be