Pirate Metrics were created by Dave McClure, founder of 500 Startups, to talk about the life cycle of users through your product. Think of it as a funnel (Figure 16-1): users finding your product is acquisition; users having a great first experience is activation; keeping users returning to your product is called retention; users recommending others because they love your product is referral; and, finally, users paying for your product because they see value in it is revenue. Put it all together and you get AARRR—Pirate Metrics. Get it?