A keycode is a numerical or alphanumeric code that represents a specific key on a keyboard or other input device. It is used in programming and software development to identify which key has been pressed, allowing applications to respond accordingly. Keycodes are essential for creating interactive user interfaces and handling user input in various software environments. In web development, keycodes are often used in conjunction with event listeners to detect keyboard actions. For example, when a user presses the Enter key, the corresponding keycode can trigger a specific function, such as submitting a form. Understanding keycodes is crucial for developers working with JavaScript or other programming languages that handle keyboard events.