DirectInput is a Microsoft API that allows applications to receive input from various devices, such as game controllers, joysticks, and keyboards. It provides a way for developers to create games and software that can respond to user actions in real-time, enhancing the overall experience. This API is part of the Microsoft DirectX suite, which is designed to facilitate multimedia and gaming applications on Windows. By using DirectInput, developers can easily manage multiple input devices, ensuring that their applications can handle complex user interactions seamlessly.