Does Do Not Disturb mode block all notifications or just the unimportant ones

On the Do Not Disturb setting in Avast, I have Silence notifcations from 3rd-party apps ticked on, which I believe is the default, whenever I have anything running full screen like Chrome, VLC, etc. But i’m wondering if this blocks all alerts or notifications, or just the non-important ones? By non-important ones I mean ones that inform me that I have a new email or a download is finished downloading, as opposed to ones that alert me if, for example, my Windows firewall is disabled.

And if it does silence all notifications, does it prevent me from seeing the notification at all even after the fact? Or does it just prevent the noise and pop up, but will still be indicated in the bottom right corner of the taskbar with the number of notifications?