Audio jacks are connectors used to transmit sound signals between devices, such as headphones, speakers, and audio interfaces. They come in various sizes, with the most common being the 3.5mm jack, often found in portable electronics like smartphones and laptops. These jacks work by plugging into corresponding ports, allowing for a secure connection. Audio jacks can carry stereo sound, which means they transmit two channels of audio, enhancing the listening experience. They are essential for connecting audio equipment in both personal and professional settings.