The free virtualization software is available in version 6.0.
With VirtualBox you can run other operating systems on your Mac, for example you can run Windows or Linux on your macOS. Which possibilities there are, we explain here. If you want to virtualize macOS on macOS, because you test a lot of software, we would advise you to use Parallels, which is very easy and also free for the mentioned use.
The version has some new features as you can read here, especially the faster graphics processing with better support for high resolution displays and macOS Guest Additions, which sounds like a macOS would be easier to set up as a guest system (but not tested yet, tip see above).
