Describe the AARRR (pirate metrics) model.

The AARRR model (also known as "pirate metrics") is a framework for analyzing and optimizing the user lifecycle in a product. It consists of five key stages:

1. Acquisition — how users find your product (advertising, SEO, recommendations).
2. Activation — the user's first positive experience with the product (e.g., registration, first use).
3. Retention — how often and how long users return to the product.
4. Referral — how likely users are to recommend the product to others.
5. Revenue — how the product monetizes and how much money it generates.

This model helps focus on key metrics that influence growth and success, and identify bottlenecks at each stage of the user journey.