These connectors are unlike any ordinary connector as they have a ground.
TRRS connectors are the audio-style connectors that you see on some phones, MP3 players and development boards. TRRS stands for “Tip, Ring, Ring, Sleeve,” which reflects the fact that, unlike a standard stereo connector, this actually has three conductors and a ground. Some devices use the extra conductor for a microphone (like hands-free headsets) or to carry a video signal (like in some MP3/MP4 players). This breakout board makes it easy to add a TRRS jack to your prototype or project by breaking out each conductor to a standard 0.1" spaced header