Many apps on mobile devices can also open these files. Safety Information

A RAR file is a compressed archive created by the WinRAR application. It is used to bundle multiple files or large folders into a single, smaller package to make transferring, uploading, and downloading faster and more efficient. To access the contents inside, users must extract the file using software like WinRAR, 7-Zip, or WinZip. The Risks of Downloading Unknown Archives

If you must inspect an unknown file for professional or research purposes, always extract it within an isolated virtual machine or sandbox environment.