Word of mouth.

Word of mouth is the passing of information from person to person through oral communication. Ancient peoples used word of mouth to tell stories and pass on traditions. The practice is also used by archivists when documenting oral histories. Word of mouth is commonly employed for advertising purposes. Advertisers use consumer incentives and social media to promote products and incite conversation among consumers. The object of word-of-mouth marketing is to communicate information about products with little to no company expenditure. Consumers have the power to popularize products simply by talking about them. When people talk about products online, it is referred to as "electronic word of mouth."