In an effort to make Windows updates easier, Microsoft removed update notifications in Windows 8 -- those little bubbles that pop up in the bottom right-hand corner. If you miss those notifications, Windows Update Notifier will bring them back.
I was never a huge fan of the update bubbles myself, but if you're picky about which updates you install, having that notification can be handy. Sadly, Windows 8 removed them, giving you only a small message in the corner of your lock screen instead.
Windows Update Notifier is a small portable app that sits quietly in your system tray, giving you a silent notification when you have updates ready to install. That's all it does: it's simple, unobtrusive and perfect for those that want a more active role in what software updates they install.