The Registry Editor is a built-in tool in the Windows operating system that allows users to view and modify the system's registry. The registry is a database that stores configuration settings and options for the operating system and installed applications. Users can access various keys and values to customize system behavior or troubleshoot issues. Using the Registry Editor requires caution, as incorrect changes can lead to system instability or malfunction. It is often used by advanced users and IT professionals for tasks such as adjusting system performance or fixing software problems. Always back up the registry before making changes to ensure safety.