It looks as if the web browser on an attached PC (on USB port) is used as the user interface to control the machine, upload design files etc. The processor controlling the machine simply serves a web page to the browser.
"They showed you then selecting a part by clicking on a file [ where from ? ] and it went away and printed."
I imagine in the video they simply used the browser to find the file on the PC, which a browser can happily do. Internet connection not needed. Basically it avoids the user having to load any specific software on his PC, all the functional software runs on the printer's own processor.
"What about where on the bed it needs to be ? Support matrix ? or % of support ?"
Apart from the mechanical construction and the user interface it looks like the operation is basically the same as the RepRap and the same principles will apply.