A credit score is a report that helps lenders determine how likely you are to pay back the money you borrow. It is based on a few different factors. Mostly, it's an evaluation of your past borrowing and payment history. If you've borrowed lots and failed to make on-time payments, your credit score will be low - this can affect the quality of the mortgage deals you will be offered. If you've handled your credit savvily, never borrowing more than you can pay back and making payments on-time for a while, you'll most likely be eligible for a fairly attractive deal and lower interest rates.