Word of mouth advertising
Word-of-mouth advertising is advertising that is distributed to consumers in an informal way and without financial ulterior motives.
Word of mouth is often called the best advertisement you can get as a company. That is because the sender is seen as objective. In practice, a lot of word of mouth is no longer word of mouth, but also digitally, for example via social media. This is also one of the reasons why social media marketing is seen as important.