Windows 10 comes with a new feature it shows all app and system notifications as toasts. The balloon notifications which were there since Windows 2000 are gone Instead, you will see a toast notification in Windows 8 style.
Enable Legacy Balloon Notifications in Windows 10
The problem with toast notifications is that they don't fade out gradually like balloons did, so if you were still reading the notification, it can disappear suddenly once the timeout is reached. For balloon notifications, you could hover over them with the mouse when they started fading away to prevent them from disappearing until you had read them. The gradual fading out gave visual feedback to the user that the notification was disappearing so he could take the mouse pointer over it to continue reading it.
If you liked balloon notifications for this reason and are not happy with toasts, you can restore balloon notifications back in Windows 10 with a simple batch script.
Below batch script allows enabling or disabling balloon notifications in Windows 10.