Typically people refer to a FICO score when taking about a credit score. The acronym "FICO" stands for Fair Isaac Company and they were the ones who came up with a specific formula to gauge an individual's credit worthiness. Your FICO score takes into account a lot of information such as your credit card payments, how long you've had a credit history, your available lines of credit, recent credit card applications, your revolving credit, and much more. You are able to purchase your FICO score from myFICO. This is the only legit site I have found as other sites trick you into signing up for their credit monitoring services.
There are three credit bureaus that have their own variations of the FICO score. Experian, Equifax, and TransUnion. Two out of the three can be purchased at myFICO.
Banks and other financial institutions look at your FICO score to make a decision on whether they want to risk lending to you and at what interest rate they are willing to take that risk on. The lower your FICO score, the higher the interest rate is going to be.
I hope this information helps you. Let me know if I can be of further assistance by clicking my profile name above.