Meta terminology
T1 / T2
Tier 1 / Tier 2
Severity tiers for inappropriate interactions with children: Tier 2 is online sexual harassment, such as sending photos of adult genitalia to a minor, while Tier 1 is soliciting or real-world harm - soliciting CEI, contact offence, and content sextortion, "the worst of the worst stuff that gives you nightmares". A November 2020 incident thread reports that thousands of minors had been reporting Tier 1 abuse, more than half of it sextortion, and "we haven't done anything".
Sources
Internal documentUnsealed internal messages ("Re: Question about the value of message data")
Internal documentUnsealed internal messages ("God knows what happened to those kids")