Dual-Tone Multi-Frequency (DTMF) is a signaling system used in telephone networks. It works by sending two specific audio tones simultaneously when a button is pressed on a telephone keypad. Each button corresponds to a unique combination of these tones, allowing the system to identify which button was pressed. DTMF is commonly used for various applications, including interactive voice response systems and automated phone services. This technology enables users to navigate menus and access services by simply pressing buttons on their phones, making communication more efficient and user-friendly.