The term is typically applied to customer acquisition, retention and monetization strategies used by newly-formed companies, which don’t have the resources to employ standard corporate marketing strategies. Growth hackers are marketers, engineers and product managers that are trained to specifically focus on building and engaging the user base of a business.[1] Growth hackers often focus on low-cost alternatives to traditional marketing, e.g. using social media and viral marketing instead of buying advertising through more traditional media such as radio, newspaper, and television.

Those people who specialize in growth hacking use various types of marketing and product iterations — rapidly testing persuasive copy, email marketing, SEO and viral strategies, among others, with a purpose to increase the conversion rate and achieve rapid growth of the user base. It can also involve on-line community management and social media outreach, driving brand experiences on social media outlets to improve performance metrics such as driving customer acquisition and selling products. It can be seen as part of the online marketing ecosystem, as in many cases growth hackers are using techniques such as search engine optimization, website analytics, content marketing and A/B testing.

Growth hacking is particularly important for startups, as it allows for at the early-stage launch face, when they focus on lowering cost per customer acquisition, whereas aiming to facilitate word-of-mouth advertising and increase customer life-time value
(source: Wikipedia)