Windows Update is a free service provided by Microsoft as part of the maintenance and support services for Windows components. The service provides software additions/modifications to fix errors or bugs, to enhance the computing experience or to improve the performance of the Windows components. An expanded version of the service is called Microsoft Update, which can also be used to replace Windows Update. Regardless of whether a computer is shared or not, the updates are applied in the same manner and are usually available for all users.
Techopedia explains Windows Update (WU)
Windows Update is available in the Control Panel feature of the Windows operating system. The update can be set to automatic or it can be configured to check for updates weekly. Windows Updates are classified as optional, featured, recommended and important. Optional updates are updates to drivers and for enhancing the user experience. Recommended updates help in addressing non-critical issues. Important updates provide favorable benefits like increased reliability, privacy and security.
Depending on the settings, Windows Update can deliver security updates, service packs and critical updates. Again, Windows Update can be configured to perform either an automatic installation or a manual installation, although important updates are usually recommended for automatic installation. Optional updates are the only updates installed manually. Windows Update provides an update history, which can be viewed by the user to determine what has been installed and the time of update. Troubleshooting assistance is also provided for failed Windows updates.
To perform its task, Windows Update requires the Internet Explorer Web browser because it uses ActiveX controls to modify the software used in the computer. Installed updates can be removed manually, but this action is recommended only when a particular update is found to be causing issues.