Windows Debugger, also known as WinDbg, is a powerful tool used for debugging applications and analyzing system crashes on the Windows operating system. It allows developers to examine the state of a program at the time of a crash, helping them identify and fix bugs. This tool supports various debugging scenarios, including user-mode and kernel-mode debugging. It can analyze memory dumps, set breakpoints, and inspect variables, making it essential for software developers and system administrators who need to troubleshoot complex issues in their applications or systems.