I’ve never really understood what credit score or rating is.
Thought it was some American nonsense.
It is one measure of how 'creditworthy' you are, calculated by taking real information on your credit file ( CCJs, loans, missed CC payments, etc) and running it through an algorithm. The real problem is that all the banks etc have their own algorithms that they keep secret. So its quite possible to have a huge score from say Experian and get turned down for a loan or CC from say HSBC.