An Extensible Operating System is a type of operating system designed to allow users to add new features and functionalities easily. This flexibility enables developers to customize the system according to specific needs without altering the core structure. By supporting plugins or modules, it can adapt to various applications and environments, making it suitable for diverse use cases. These systems often provide a framework that encourages third-party developers to create extensions. Examples include Linux distributions and Android, which allow users to enhance their experience through additional software. This extensibility fosters innovation and keeps the operating system relevant over time.