Growth hacking is a marketing technique used by startups that focuses on creativity, analytics, and social metrics to gain exposure and sell products. It involves tracking key metrics around user acquisition, activation, retention, referrals, and revenue. Acquisition focuses on how users first come to the site. Activation tracks user behavior on first visits. Retention measures how often users return. Referrals look at how users share the product. Revenue examines how the company generates money. The goal is to acquire users through various channels, engage them on initial visits, encourage repeat visits, promote sharing among networks, and ultimately create monetization opportunities.