A number that helps businesses decide how likely you are to repay a loan to pay your bills on time. The higher the number, the easier time you're going to have getting financing and loans.
Your credit score is based on your credit report and on your history of repaying stuff on time. It's important to take good care of your credit score because once it plummets, it can take years to rebuild again. If you have a good credit score (750–800), you're going to have an easier time getting loans and you'll get lower interest rates on the loans you get. Consider it good karma.