This document discusses growth hacking and defines what a growth hacker is. It explains that growth hacking focuses on finding low-cost marketing strategies to help startups grow, as traditional marketing channels are expensive and saturated. A growth hacker's main goal is growth, and they follow a cycle of experimenting with different strategies, measuring their effectiveness, and optimizing the top-performing ones. The document provides some examples of growth hacking techniques used by companies like Airbnb and Dropbox. It concludes by providing resources for learning more about growth hacking and contact information for the author.