it have different window but still 1 file opened, i think if i know how to make like that it will make more easy when use blender thank you
that window is just a render window , its like when you press f12, a render window will appear and start rendering.
The owner of the file leaves that window open and saves the file, so when you open the file the window is still there but empty, because the cache file is in his computer and not in yours.
I see that you are using blender 2.79 in blender 2.83 or later , there's an ability to split the viewport and change one of the viewport to a rendered view like this:
it's definitely a much faster way to work
i really would suggest for you to upgrade your blender version to the latest one, and maybe update your windows version to windows 10 too