Credit scores, ranging from 300 to 850, are calculated using models like FICO and VantageScore, assessing payment history, credit utilization, credit history length, new credit, and credit mix. Understanding these factors—payment timeliness, debt levels, account ages, and types of credit—can help improve your score. Late payments, high utilization, and new inquiries can lower it, while a diverse, long-standing credit history can raise it.