BitBox is a web browser installed on a virtual machine
BitBox comes with its own copy of VirtualBox that is running a reduced OS and that OS has a choice of browsers installed
you can have BitBox Firefox/Chrome
BitBox is the most secure browser you can use on your device
whatever website you browse inside BitBox your original OS won't get affected once you close BitBox Firefox/Chrome it gets reset
should note:
As for how secure that is, for the most part, it's the same as running a browser inside a Linux VM in VirtualBox with a snapshot you roll back every time you want to reset
and probably easier for folk to set up BitBox for browsing than actually setting up VirtualBox, or a VM, software
While a virtual machine does add security, virtual machine breakouts do exist, and VirtualBox has been on the receiving end of such exploits before