Deductions & credits

Thanks! Very helpful! One more quick question - are these credits considered non-refundable? If I understand non-refundable vs refundable, then a non-refundable credit would mean that I can take it off if I owe taxes but if I'm already getting a refund, it won't increase the refund and I would have to save it for a future year when I might owe taxes.  Is my understanding on that correct?