Ever since the dawn of the modern Windows environment (from Windows 95 on), notification balloons have been used for all kinds of system information. Everything from update notifications to USB device status, security alerts, amongst others.
The ones that come from the operating system can be particularly annoying. Especially if you know what you're doing.
For example, if you use my Windows Update Disabler, you've made a conscious choice to ignore Windows Updates. But the system will still show you balloon notifications trying to goad you back into Windows Updates. Solution? Disable balloon notifications too! My utility will do just that.
Keep in mind, this application will disable SYSTEM notification balloons. It does nothing for application notifications (called Toast Notifications). Run it once to disable Notification Balloons, again to re-enable them.