These are file types that you can save and open in Minitab.
With the release of Minitab 19 and tabbed output, Minitab saves projects as MPX files. You cannot open MPX files in versions of Minitab that do not support tabbed output.
With the release of Minitab 19 and tabbed output, Minitab saves worksheets as MWX files. You cannot open MWX files in versions of Minitab that do not support tabbed output.
In the web app, you cannot open XLS and XML files.
You can save text files using either ANSI (sometimes called ASCII) or Unicode encoding. ANSI is the older standard. Unicode was developed to represent more characters and to be independent of the computer's regional settings. Some older applications might support only ANSI.