Viral marketing 

Viral marketing or viral advertising is a marketing technique that uses pre-existing social networking services and other technologies to produce increases in brand awareness or to achieve other marketing objectives through self-replicating viral processes, analogous to the spread of viruses or computer viruses. It can be delivered by word of mouth or enhanced by the network effects of the Internet and mobile networks. Viral advertising is personal and, while coming from an identified sponsor, it does not mean businesses pay for its distribution. Most of the well-known viral ads circulating online are ads paid by a sponsor company, launched either on their own platform or on social media websites such as YouTube.