A headphone jack is a socket found in audio devices that accepts pin-shaped headphone plugs. That works by transmitting an audio signals from an audio device to headphones by providing an electrical contact between the two. The most common type of headphone jack accepts 3.5mm plugs, also referred to as "mini jack plugs" and "1/8-inch plugs." The 3.5mm headphone jack or socket is standard on most handheld electronics with limited space, such as Mobile phones, digital audio players and vidcams. Netbooks and laptops also use this configuration, as do internal desktop audio cards. Advanced sound cards geared towards recording music often feature a separate patch bay with a full-sized headphone jack and inputs for musical instruments and microphones.  A headphone jack is typically located on the top or side of portable devices.

The pupose of headphone jack is used to connect the headphones are personal speakers.They allow the person to hear sound from an audio device without others around them hearing it. They are commonly used to listen to audio through portable music devices, Mobile phones, tablets. They can also be found on stereos.

According to name convention, a 1/8-inch (3.5mm) headphone jack is an audio socket that accepts a 3.5mm male pin or audio plug. In electronics, a phone connector is a common family of connector typically used for analog signals, primarily audio. It is cylindrical in shape, typically with three contacts, although versions with two or four contacts are also common. Three-contact versions are known as TRS connectors, where T stands for "tip", R stands for "ring" and S stands for "sleeve". Similarly, two- and four-contact versions are called TS and TRRS connectors respectively.The 3.5 mm or miniature sizes were originally designed as two-conductor connectors for earpieces on transistor radios.