Disk Cleanup is a built-in utility in Microsoft Windows that helps users free up space on their hard drives. It scans the computer for unnecessary files, such as temporary files, system files, and items in the recycle bin, which can accumulate over time and take up valuable storage space. By removing these files, users can improve their system's performance and create more room for important data. To use Disk Cleanup, users can search for it in the Start Menu and select the drive they want to clean. The tool will then present a list of file types that can be deleted. After selecting the desired files, users can click "OK" to remove them, making their computer run more efficiently.