Ask HN: What's happening with Google accounts Friday?

I know something is happening with Google accounts entering a new level of security Friday. I don't know what is involved, and I've heard rumors this includes things like shutting down IMAP/POP3 access to GMail. Can someone explain, because my Googling skills, ironically, have failed and I feel like I'm hearing the results of 10 levels of signal corruption like through a game of telephone.

The only thing I'm fairly sure of is that it in some way relates to third-party apps. But I don't even know if that means people who use alternative email clients or apps who use Google OAuth2. I also heard that iPhone based accounts have a longer period of time, but that also seems possible.

Thanks.