I bought my first Apple computer on Thanksgiving night, 2006, at one of those “early Black Friday” sales at some now-defunct computer chain. It was a HUGE (by the standards of the day) 24″ iMac that was near the top-of-the-line in terms of their technology offerings back then.
One of the things I planned to use it for was audio recording and production.
Like most Macs, it had two 3.5mm jacks on the back, one for a mic/line input and one for headphone/speaker output.
Several years earlier, I had purchased a small portable A/D unit for recording stuff using “stealth mics”, and it has an optical digital (S/PDIF) output. I went to the Apple store and asked the “geniuses” there what I needed to plug it into my fancy new iMac.