A Singleton is a design pattern used in software development that ensures a class has only one instance throughout the application. This is useful when exactly one object is needed to coordinate actions across the system. For example, a configuration manager that holds application settings should be a Singleton, so all parts of the program access the same settings without creating multiple instances. In practical terms, a Singleton typically restricts instantiation by making its constructor private and providing a static method to access the single instance. This pattern is commonly used in various programming languages, including Java, C#, and Python, to manage shared resources effectively.