Child Sexual Abuse Material, basically the current term for child porn. [email protected] is completely right on all of it. There is a missing detail that loli (along with a few other questionable/objectionable subs) were banned from LemmyNSFW, and went to a different one that promised to be less restrictive, and is widely defederated because of it.
(Side note: While it can be difficult/impossible to draw the line based on appearances, these were clearly and obviously meant to be depictions of children, and often very young children)