audio input?

That's a lot of assumptions from a one-line post asking for options to input audio. Which is fine as long as an impression is not left that normal headsets won't work with the mini's headphone input. They of course do, and for speech the quality is excellent.

That said, I grant that Apple's documentation, both in their spec and also their Essentials handbook, leaves room for ambiguity. Bottom line is this: the headphone port comes with an integrated mic (splittable using a splitter), but it's (obviously) not good for professional audio. Apple should update their spec and documentation...

Yes, it’s the mic input integrated into the headphone jack. You can split it to sound out and mic in.

You will need an audio to USB interface. The best place to ask about that is in the Garageband forum.

Yes I confirm. The screenshot is what shows with a headset attached to the headphone port with the mic in use. It's obviously a mic input.

Thanks. As I suspected this is for a headset, so it only works with that sort of connector. As a mic input it's not suitable for line-level audio input (which I would guess is what the OP wants) because you'd have to reduce the input level down to a few millivolts to avoid overloading the input and it would then be amplified again, which would do nothing for the noise level. Of course if he just wants to record speech it might be OK, though I'd be dubious about the quality.

Apple's downgrading of audio outputs and inputs is irritating. My older iMac, from 2008, has an optical input making it possible to make high quality recordings: in my experience the old line level inputs were too noisy for high quality work. Now you have to buy an interface, and they have become a good deal more expensive than when I bought the Edirol model I use for my later iMac.

Yes, it’s the mic input integrated into the headphone jack. You can split it to sound out and mic in.

This is the case with some older Macs, but no mention is made of the tech specs: it would be useful if you can confirm that it is actually the case. If so I would assume that it's a line level input, not a mic input, as has been the case previously, unless it's a headset input/output.