Customer retention is crucial for businesses as it increases profits by 25-95% with a mere 5% increase in customer retention. Retention can be measured using churn rate, which helps determine the effectiveness of retention strategies and their ROI. Key metrics to track include customer retention per cohort, lifetime customer value (LCV), Net Promoter Score (NPS), and customer engagement rate. These metrics provide insights into customer behavior, satisfaction, and loyalty, enabling businesses to improve their products and services accordingly. Effective onboarding, instant customer service, and putting customers first are some strategies that can boost retention metrics.