A "Blue Screen" refers to a critical error screen displayed by the operating system, particularly in Microsoft Windows. It indicates that the system has encountered a problem it cannot recover from, often due to hardware or software issues. This screen typically contains a message that helps users identify the error, along with a stop code for troubleshooting. When a Blue Screen occurs, the computer usually restarts automatically after a brief display of the error message. Users may experience data loss if unsaved work is present. Regular updates and system maintenance can help reduce the frequency of these errors.