Child tax credit?

I was filling out a W-4 form at work the other day—seeing as we have another tax deduction now—and I noticed a section entitled Child Tax Credit. Apparently, we fall within the criteria which would nearly double the number of exemptions for which we qualify.

However, I did not take the extra exemptions because I was afraid of taking too many. So what’s the deal? What is this Child Tax Credit?

Are there any tax professionals in the audience who can explain it in layman’s terms? Of course, I would abide by the proviso that it would be purely for information purposes only, that I would not hold you liable for subsequent actions I take, and that I will consult a tax professional in my pay before taking any action. Just to satisfy the lawyers, like.

That said, can someone translate?