Used to be called Quiet Hours, Focus Assist is an improved feature in Windows 10 April Update to help you stay in the zone. It’s a smart way of stopping notifications popping up when you are busy. By default, Focus Assist will automatically mute all notifications when you are playing a game or presenting a PowerPoint presentation to a projected screen.
There are a few ways of engaging Focus Assist in Windows 10.
You can open up the Action Center and click on Focus Assist button to toggle through three defined settings, Priority Only, Alarm Only, and Off.
Or simply right-click the Action Center icon on the taskbar, and choose Focus assist.
Switching to Alarms only mode hides all notifications, except for alarms. But if you still want the important notifications to get your attention during the quiet hour period, you can create a priority list by going to Settings > System > Focus Assist and clicking the Customize your priority list link.
You can also set it up to turn on Focus Assist automatically at certain times during a day. Go to Settings > System > Focus Assist, and set it up the settings under Automatic rules section.
Also, by default, a summary of notifications of what you’ve missed while you were working will pop up as soon as the Focus assist is turned off so you can catch up quickly what’s been missing.