An "Input Event" refers to any action that a user performs to interact with a computer or device. This can include actions like clicking a mouse, pressing a key on a keyboard, or tapping a touchscreen. Input events are essential for user interfaces, as they allow users to communicate their intentions to the system. When an input event occurs, the system processes it to determine the appropriate response. For example, when a user clicks a button on a web page, the input event triggers a specific function, such as submitting a form or opening a new window. This interaction is fundamental to how users navigate and utilize software applications.