Credit scores come from FICO, which is based off of payment history, current debt, types of credit used, as well as, length of credit history. Each lender interprets scores differently. Typically, any score above 750 is considered excellent, 650 is fair and anything around or under 600 is poor. The higher the score, usually the better the interest rate consumers gets.
To improve scores, be sure payments are timely; keep balances as low, and avoid applying for new cards because your score will drop for each application. Check your report annually for any inaccuracies. Reported wrong information can have a serious effect on your credit future.