Basically it means assuming that small babies have an awareness of their elimination needs and will attempt to communicate them with us, as part of an instinct to avoid soiling themselves/their caregivers/their sleeping space. (Then they gradually lose that awareness as they are trained to just go in their diapers wherever/whenever, and only get it back later in what we now think of as potty readiness)
So all we do is try to learn baby's signals and offer a potty opportunity if we think he might want one - we have a little potty that he can sit on (with us holding him up of course) or he'll go in the sink too. There's a sound association we do, a 'sssss' noise, that helps cue him that it's OK to go. It's 100% non-coercive, we just say 'Hmm, I wonder if you need the potty' and if he goes, great, if he doesn't, great, if we miss it and he goes in his diaper, great, everything is fine. It's all about his comfort and trying to respond to his needs.
And he loves it as far as we can tell, he seems to much prefer going in the sink or potty than in his diaper, and will fuss and hold it for a couple of minutes while we get him undressed and in position, then go as soon as we cue. Big smile, clean diaper goes back on and he's happy as a clam.
There are lots of different ways to do it, we read the book Go Diaper Free by Andrea Olson and that got us started. (The title is misleading in that it doesn't mean zero diapers - we still have LO in them all the time we just put the clean one back on after pottying)
Anyway that's about the gist of it! I thought it would be a giant hassle and super hard but it's been so easy and relaxed. We catch some pees/poos, miss lots, take breaks whenever, it's all good.
It's been lovely for DH as well because I'm breastfeeding (and LO often feeds to sleep) so he used to feel like he couldn't really do anything to meet LO's most basic needs you know? But now he can as we're both equally able to offer the potty.
So yeah! We're really liking it and LO seems happy and comfortable, so it's a win all around.