If you live in the US and are over 18 years old, chances are you have a credit score.
Basically, credit is an agreement to borrow money and make purchases but pay back the entire amount within a certain timeframe. A credit score basically tracks and "scores" you based on how well you're able to do that, and helps lenders assess your level of risk as a borrower. In the US, a strong credit score is crucial for opening a new credit card, buying a home, etc.
And TBH, they're kinda awful and (IMO) don't actually help anyone. Here's why:
Finally able to pay off your student loan and be in less debt? That's gonna hurt your score: