DTMF, or Dual-Tone Multi-Frequency, is a signaling system used in telecommunication. It allows users to send information by pressing keys on a telephone keypad. Each key generates a unique combination of two audio tones, which are transmitted over the phone line to the receiving system. This technology is commonly used in telephone systems for functions like navigating automated menus or entering account information. DTMF tones are easily recognizable and can be processed by various devices, making it a reliable method for communication in both landline and mobile networks.