What is the avast! Silent/Gaming Mode?
At various times while your computer is running, messages may be displayed on your screen e.g. when the virus definitions have been updated, when an incoming e-mail is being scanned etc. This can result in full-screen applications (e.g. games) being interrupted as Windows switches from full-screen mode to normal mode when the message appears. You can specify that messages will never be displayed, or will not be displayed if a full-screen application is running."
You are still protected only shutting of these notifications.