The Child Tax Credit can reduce your federal income tax due by $2,000 per qualifying child. You’ll only be able to claim the Additional Child Tax Credit if the amount of your Child Tax Credit is more than the amount of income tax you owe. In that case, you may be eligible to claim up to $1,400 per qualifying child on the Additional Child Tax Credit, as a refundable credit (meaning it can increase your refund even if you don’t owe any tax).
Credit Karma Tax will automatically calculate these credits for you if you qualify based on the information you provide.
If you are curious about the specifics of the Child Tax Credit, you the IRS provides more information at About Schedule 8812 (Form 1040), Additional Child Tax Credit.