Pirate metrics is essentially a way of categorizing different metrics and KPIs, and is made up of the metric stages which can be referred to as AARRR - Acquisition, Activation, Revenue, Retention and Referral. Many companies track metrics by the funnel, and then try to improve conversion rates from one of these stages to another. The AARRR metrics model was developed by Dave Mcclure and represents all of the behaviours of customers.