How customers interact with your marketing materials (like emails and website) and product. This data is usually managed using different tools for marketing and product analytics.
Most founders drown in data but are starved for insights. Data is useless if you don't use it to change your behavior. If your data shows people are leaving at the pricing page, stop looking at the numbers and start looking at the Messaging-Market Alignment. Data should tell you where the problem is, not how to fix it.