How to Identify and Run a File with an Unknown Extension

Ever got stuck with a file that has some mysterious extension? Where no matter how much you try, the Jigsaw puzzle doesn’t seem to fit together? So, for instance, if the file has the extension (characters after the last period in the file’s name) doc or docx, you know you need Microsoft Office or its alternative productive suites such as LibreOffice or Google Doc to view and edit that file. But what if the file extension is something you have never heard of before, or something your computer can’t decide the appropriate software for?
How to Identify and Run a File with an Unknown Extension