A credit score is a number between a range, with the top of that range being the best possible score. It is calculated using your Credit Report, based on how you manage your finances and how much credit history you have from the UK over the past 6 years. When you apply for credit – such as a credit card, loan or hire purchase on a car – the lender takes a look at your credit information.
That information includes things such as whether you make payments on other accounts on time, the credit limits on your credit and store cards, and how many applications you've made for credit recently.
They use this information, along with what you've put on your application form and details they have if you're already a customer, and give you a credit score. The higher your credit score, the higher the chances you will be accepted for credit. You don't have just one credit score because different lenders use their own scoring systems.