i.e. it starts a command prompt and runs that batch file to set up the
environment so that Modeller will work. (If you run a regular command
prompt, it won't have the paths set up properly, and Modeller won't work.)
I don't know why the Start menu shortcut isn't being installed on your
system - although you have to run the installer as an admin user in
order for it to do that (it should warn you if you don't) - but you can
make your own shortcut to Modeller in this case.