Oral and spontaneous method of transfer between people, often regarding opinions or rumors. Word of mouth can concern a product a service or a company, and it can be positive or negative.
By extension, the term designates recommendation phenomena whether they are oral or not, for example when they use other communication tools such as social media, blogs, forums, review websites.
Word of mouth leads to a movement of promotion or denigration with huge consequences : this is referred as buzz or viral marketing.
A customer experience strategy that aim to optimize word of mouth reduces costs of acquisition of new customers.