A RAR file is a compressed archive format. Much like a .ZIP file, it is used to "pack" multiple files into a single, smaller container for easier sharing or storage. To open it, you generally need software like WinRAR or 7-Zip. Potential Origins of "SPECIAL1061_PACK9.rar"
RAR files are frequently used to hide .exe or .js files that can infect your computer once extracted.
Many "Special Packs" found on forums are password-protected to prevent antivirus software from scanning the contents.