Windows Update is a Microsoft services available on Internet to scan your computer and provide you with a tailored selection of updates for your Windows PC.
During the scan, a list of categories appears under Welcome to Windows Update and the number of updates that are available in each category is noted in parentheses.
Critical Updates are important!
Any update that is critical to the operation of your computer is considered a "Critical Update," and is automatically selected for installation during the scan for available updates. These updates are provided to help resolve known issues, and to protect your computer from known security vulnerabilities. Whether a critical update applies to your operating system, software programs, or hardware, it is listed in the "Critical Updates" category.