Please explain tax credits to me (US)

I feel like I have a basic understanding of tax credits, but nothing so far as would make the most sense in what I want to know: I'm looking into buying a new car, and it looks like I can get a 7500 tax credit for the car I'm interested in buying. My understanding is that these credits are "non-refundable" meaning I don't actually get that money back, but how does it still work? I pay into the income tax (I know, I don't want to know the benefits of doing this vs not, it's just easier for me to pay more and get some back when the time comes), so I always get a refund. Would my refund be higher then because I get a credit on the taxes that I paid in? Or would it be the same and my tax liability would be reduced?

I need someone to explain this to me like I'm 5, please!