In other words, within your browser, it enables a new connection to a hosted virtual machine (VM) that emulates a physical computer’s processor. This process enables the virtual machine to run a variety of guest operating systems using your Web browser as the display monitor.
The VM display is provided by a direct virtual network computing (VNC) connection. VNC is a graphical desktop-sharing system using the remote frame buffer protocol (RFB) to allow remote control of another computer. Multiple users may connect to the VNC server at the same time.
A button sits in the center of the left window edge of the running distro. Click it to slide out a menu with several options for controlling the VNC display window.
Article on how DistroTest works: https://linuxinsider.com/story/How-to-Distro-Hop-With-a-Web-Browser-86178.html
That’s very informative, thanks!
For others curious: