Well, i meant to use Eicar to check whether the AVG Resident Shield is really disabled, but anyway:

“Scan file on open” means scanning the file when “opening the file for reading or writing”. It means, for example, that it is scanned when you open the Eicar.com file in Notepad. Of course, if you doublelick (execute) the file, it is read (and scanned) as well.

However, even when you disable “Scan file on open”, it is still scanned when you try to execute it (i.e. on doubleclick) - that’s the first page of the Standard Shield settings - “Scanner (Basic)” - Scan executed programs. However, it wouldn’t be scanned in this case if you open the file in Notepad.