MSI MS-6151 Manual page 42

You can connect joystick or game pads to this connector.
Joystick/MIDI
Line Out is a connector for Speakers or Headphones. Line In is used for
external CD player, Tape layer, or other audio devices. Mic is a connector for
the microphones.
Line Out Line In Mic
1/8" Stereo Audio Connectors
2-36