HijackThis is a system analysis tool that scans a computer's system and browser settings to identify potentially harmful software. It generates a detailed log file of all processes and browser add-ons running on the system, allowing users to identify and remove any suspicious items. The software also includes a feature for creating backups before making any changes to the system, ensuring that users can easily restore their previous settings if needed. Lastly, HijackThis allows users to share their log files with online forums to get help identifying and removing any potential threats.