Windows 10 doesn't ship with the software to play DVDs. If you want to make that happen, Microsoft thinks you should spend $18.39 (Australian) on a Microsoft DVD-playing app from the App Store. Don't do that.
It's kind of a shame that there's no built-in software to play DVDs on Windows 10 -- one more thing to download for your grandparents! -- but as anyone who's wrestled with Windows Media Player knows, there are much better options out there anyway. VLC costs nothing, has a better user interface, and costs exactly $18.39 less than Microsoft's offering.