"Word of mouth" refers to the transmission of information from person to person through oral communication. It is an informal way of sharing information, recommendations, or opinions about products, services, events, or any other topic.

In essence, it's like a personal recommendation or testimonial that is passed on through conversations. Because it comes from someone known and trusted, word-of-mouth can be a powerful influence.

Word-of-mouth is often considered a credible form of advertising because people tend to trust the opinions of their friends, family, and acquaintances more than traditional advertising methods. This makes it a very valuable marketing tool for businesses.

For additional information, see these resources:

• Investopedia - Word-of-Mouth Marketing