This document provides an overview of growth hacking by defining what it is, explaining its history and key concepts. It describes growth hacking as having an obsessive focus on growth above all else. The term was coined in 2010 to describe entrepreneurs who use non-traditional marketing tactics to achieve rapid user acquisition and retention. Examples are given of how AirBnB leveraged Craigslist to grow their user base by reverse engineering Craigslist's platform without an API.