About the audio ports on Mac
Your Mac includes one or more audio ports. You can use these ports to connect to headphones (which may include a built-in microphone), self-powered speakers, or an audio system.
Other ports can transfer audio data as well. Some headphones, microphones, speakers, and audio interfaces connect to your computer’s USB, Thunderbolt, or Ethernet port. Video ports transfer both audio and video data.
Note: There may be an identifying icon near each audio port, depending on your Mac.
Headphone: You can use this port as a combination headphone and line-out port. Connect headphones (with or without a built-in microphone), self-powered speakers, or other audio equipment using a standard audio cable with a 3.5 mm metal plug.
Audio in: You can use this port to connect stereo equipment to your Mac with a stereo miniplug-to-RCA cable adapter. Some Mac computers also support optical digital audio input using the S/PDIF protocol. Use a Toslink cable with a Toslink miniplug adapter or a fiber-optic cable with a 3.5 mm plastic or nylon optical plug.
Analog audio out: You can use this port to connect self-powered speakers or other audio equipment using a standard audio cable with a 3.5 mm metal plug.