How are the audio input and output of a transceiver connected in a station configured to operate using FT8?

FT8 is a highly popular digital mode that operates using audio tones. To operate FT8, the radio must send received audio to a computer for decoding, and the computer must send generated audio tones back to the radio to be transmitted. This is simply achieved by connecting the audio output of the transceiver to the audio input of a computer, and the audio input of the transceiver to the audio output of the computer. A computer running specialized software (like WSJT-X) does all the encoding and decoding directly via its soundcard, so no external 'conversion unit', terminal node controller, or internet website is required.