1. WOM is a channel. This is a great way to describe it if your audience is people who understand traditional media planning and think in terms of impressions and CPCs.
2. WOM is an outcome. Think of this as "conversation-based marketing." When WOM is treated as an outcome of all your acitivities, you can start to think more broadly about what your marketing is doing.
3. WOM is viral/buzz. This is one of the most common perceptions about WOM, that it is all about having something go viral or building a buzz. The way I usually describe the difference is through the importance of belief. Viral or buzz marketing is all about having one person pass something along to someone else for any quality (not necessarily one that is around the brand). WOM on the other hand, typically involves some kind of belief.
http://www.dmwmedia.com/news/2008/05/13/analysis:-3-philosophies-word-mouth-marketing
