Hmm, new to PCs I see? Yes, .rar files are a type of compressed file. They are like a folder that is "zipped" up into a neat little package, making it easier to deliver and download. The .rar file can be extracted using WinRar or 7zip. If you don't have either of these programs, you will need to download and install them.
If you were trying to use this on a phone, then check again. This is for Windows.
If you are under 18, then check again. This is for adults.