What a credit score actually is
When I landed here at 18 I thought a credit score was a bank account balance. It is not. It is a number that predicts how likely you are to pay back borrowed money, and almost everything else about borrowing flows from it.
What it measures
Scores (FICO and VantageScore are the common ones) run roughly 300 to 850. The biggest pieces are your payment history (do you pay on time), how much of your available credit you are using, how long your accounts have been open, your mix of credit types, and how many new accounts you have opened recently. Payment history and utilization carry the most weight.
Why it matters
A higher score means cheaper money: lower interest on a car loan, approval for an apartment, better credit cards, sometimes lower insurance. A thin file (little or no history) is not bad, it is just empty. The goal early on is simply to start filling it with on-time payments.
Where to see it
Many banks and card apps show your score for free, and you can pull your full credit reports for free at annualcreditreport.com. Checking your own score is a soft pull and never hurts it.