Fifty percent off your purchase here. 1,000 free miles there. When it comes to credit cards, the benefits are easy to see — while the downsides are often buried in the small print on the application.

But in order to fully maximise your credit card benefits (and minimise the damage), you have to know how they work. And the first rule is that those perks are not the main purpose of your plastic. "The point of a credit card is to build your credit score," explains Priya Malani, Refinery29's financial expert. "Think of your credit score kind of like a 'report card' of how reliable you are to pay back a loan." The better the score, the greater your chances of getting a mortgage, having a rental application sail through, or even getting a job. (It's totally legal for hiring managers to do a background check that includes your credit score; fair or not, some hiring managers assume a solid credit score means you'll be a solid employee.)

Sounds like a huge deal? It is. That's why it literally pays to know everything you can about credit cards before you slide one in your wallet. Click through to find the advice we wish we'd had before we opened a credit card.