This may help. I know my cousins play it occasionally (including one that doesn't really play videogames). Seems like a traditional 2-D side scrolling level grind fest common to a lot of the free Korean MMO. I'm pretty sure the system requirements are rather low considering the N64 quality animation.
My early teen daughter was really into it, so my son and I made some characters, too. I think a large part of the attraction was the fact that some of her friends from school were also on it. She fomed a guild and made some "web friends." The other attraction was killing enough monsters and performing quests to go up in level to get more abilities (to help you kill monsters and perform quests....). There are special holiday themes where some monsters change appearance and new quests and new items are available.
In general you walk around an animae world and kill monsters and chit chat with other users. Not particularly inspired, but it could become strangely addicting to "just get that one more level."
They make some effort to control inappropriate language and users can get banned for cheating or inappropriate messaging.
I'd say it's safe enough, but not particularly engaging outside the social aspect.