are you asking what is meant by credit score? if so it's a rating of you credit worthiness. the higher the score the more likely you can get loans and credit cards, lease or finance a car, buy or rent a home.
low credit scores generally carry higher interest rates if you can get a loan including credit card at all.
there are many rating agencies and your scores will differ because different formulas, dates and history are used
the three most critical factors are
lack of Derogatory marks - late payments, debt not repaid, eviction, default judgments, etc
credit history - timely payment over a period of time the longer the better
revolving credit usage - credit cards, lines of credit and the like, best if usage under 30%
for FICO purposes these items nake up about 80% of your score