Chokers

I'm completely up to date with the manga and have been for a while, but they brand up the significance of the chokers when I went back a few chapters (I went back chapters because I stopped reading it for a month and then when I picked it up from my break I didn't know what chapter I was on so I read from when rudo turned the box into a jinki, is that what you call something rudos changed? So yeah after they got the information broker they emphasised on the chokers, how did they get them and why are they bad/what do they do?