Your entire spending history is detailed in credit reports. Potential lenders can obtain this credit report and have access to your payment habits with utilities companies, school loans, car loans, mortgage payments, lease payments, and credit card bills. Not only can these creditors see your payment history, but they can also see the amount of debt you have in relation to the amount of credit that you have available to you. All of these factors work together to determine your score. If you have been irresponsible with your bill payments, and you have spent well outside of your financial means, then your score will suffer. This lets potential lenders know that you are a risk, and you could suffer the sting of a rejection, or end up with interest payments that add thousands of dollars to the cost of a large purchase.
Your habits are reported to three major bureaus: Equifax, Experian, and TransUnion. For the most part, these three bureaus keep separate credit histories, and what you find reported there depends on which creditors use what bureau. For instance, a retail store may only check the Experian report, which means that you will only be reported to Experian for that particular creditor. Larger lenders, however, will check all three bureaus. This is true for car, mortgage, and education loans. By defaulting on any of these loans, you can expect your score for all three bureaus to suffer.
Be sure to check your reports regularly. By doing so, you can be sure to remove any errors from your credit history, which can drastically improve your scores almost immediately. If you see that there are consequatory reports on your credit report, it is a good idea to contact the lenders in question to negotiate payment terms or pay off the loan in order to remove the bad reports from your credit history as soon as possible.
Your credit score is definitely the most important part of your credit report. Do not be fooled into thinking that a good credit score will gain you automatic approval, though. Potential lenders check everything on your credit report, and one missed payment on your record could mean the difference between a lower interest rate and an outright credit rejection. Take responsibility for your credit rating, and actively work to keep it healthy.