Tracking key metrics is important for ecommerce companies to analyze business performance and customer behavior. Some important metrics include sales conversion rate, customer acquisition cost, revenue by traffic source, new vs returning customers, conversion by device type, cart abandonment, percentage of returning customers, average order value, customer lifetime value, customer retention rate, average order size, email engagement, Google search performance, social media conversion rate, and number of transactions. Understanding these metrics can help companies improve marketing strategies, lower costs, increase sales and optimize the customer experience.