You’ve probably seen something like this flying in from the top right edge of your screen:
That’s an “alert.” Alerts (and their cousins, the Banners) are handy, but the default settings put far too many onto your screen. You don’t need a notification for every incoming email, do you? (No, you don’t.)
So… adjust the settings.
Apple Menu/System Preferences/Notifications.
Work your way through the apps on the left and configure the “Alert Style,” on the right. Each app gets its own settings and there is no way to change them all at once (although Do Not Disturb will let you turn off alerts and banners altogether). For emails you might choose a Mail Alert Style of “None,” like I did.
Tell a friend. Use the “Share” buttons