XP- can someone help me understand Additional Child Tax Cre?

[ProfessorArtNerd]

I just checked the status of my refund, since I filed and fed was accepted Jan 27.  It says that those who qualified for EITC and/or Additional Child Tax Credit wouldn't get their refunds til the end of February.  Only I don't have any idea what Additional Child Tax Credit is, or why I'd qualify.  (I know it's not bc of EITC).

I googled, but I just couldn't follow.  Help?