A credit score is a three-digit number which helps lenders decide whether to give you credit. One way of thinking about it is to see it as a measure of risk to the lender. The higher the score, the better you managed your debt in the past, which makes it more likely that you will be considered low risk and therefore given a loan, or viewed favourably by a potential employer or property landlord.
A higher score means that your application is more likely to be accepted. It also means that you could be eligible for better interest rates and better deals when borrowing money or taking out a mortgage.