In marketing and specifically online, the term "viral" refers the spread of a video, website, photo or another message in a rapid and far reaching way. The message travels in a viral way, similar to that of a real virus or a computer virus - seemingly reaching everyone in its path. It is based on the concept that ideas can spread like a virus.
Certain tools exist to help accelerate marketing messages, thus increasing the odds of a message "going viral". Social media is one of the most powerful tools in viral marketing. Some WordPress plugins, such as Contest Domination, harness the power of social media by encouraging and rewarding individuals to share a specific marketing message. The result is that everyone who receives the message feels compelled to share it again.
A true viral video (or message) doesn't require incentives other than the video itself to encourage sharing.
Planning a successful viral campaign is not an easy task. However, there are some things you can do, to increase the odds of success: