Credit scores are calculated based on 5 main factors: past delinquencies (35%), debt ratio (30%), average age of credit files (15%), mix of credit (10%), and inquiries (10%). A higher credit score indicates a lower statistical risk of defaulting on a loan within 90 days. Scores range from 300 to 850, with higher scores associated with lower interest rates and long term savings on loans. Maintaining good credit through on-time payments, low credit utilization, and a history of managing different credit products responsibly can help increase one's credit score over time.