Growth hacking is a concept that promotes constant experimentation across various departments of business like marketing, business development etc, to determine the most effective way to do business.
An important objective of growth hacking is to grow business massively in a short span of time. It is a commonly adopted strategy by startups.
Here is an article where you can read about growth hacking strategies and the phases of growth hacking. Link to the article: https://www.feedough.com/growth-hacking-an-actionable-guide/