An audio jack is a small connector used to plug in headphones or speakers to devices like smartphones, laptops, and music players. It allows sound to travel from the device to the audio equipment, enabling you to listen to music, watch videos, or make calls privately. The most common type is the 3.5mm jack, which is found on many devices. These jacks come in different sizes and types, such as the TRS (Tip-Ring-Sleeve) for stereo sound and the TRRS (Tip-Ring-Ring-Sleeve) for both audio and microphone functions. Despite the rise of wireless technology, audio jacks remain popular for their simplicity and reliability.