A file ending in .rar is a file. It is a proprietary format used for:
Could you provide on where you found this file or what you believe its contents might be? xROUS.rar
Including redundancy data to repair damaged archives. Safety Precautions for Unknown .RAR Files A file ending in
Reducing the size of one or more files to save storage or make them easier to transmit. xROUS.rar
Protecting contents with AES-128 or higher bit encryption and password protection.