Viral marketing
Also known as: viral marketing
Freely translated, viral marketing is a form of marketing that spreads like a virus (viral). Basically, it is word-of-mouth advertising(buzz) which can reach a large number of people in a fast and inexpensive way (if done properly) due to today's communication capabilities and speeds.
By spreading, think of sharing via social media, among other things. When content is created with the goal of being spread across the Internet, we also speak of linkbait.