Earned media
Earned media (or free media) is content relating to a person or organization which is published by a third party. It includes articles by media outlets, interviews with the person or representatives of the organization, or bylined editorials in trade press and other publications. It may also include social media sharing and unpaid mentions by podcasters. Earned media excludes paid publicity gained through promotional efforts such as advertising (paid media) or through company branding (owned media). Background
Marketing communication can be summarized as falling into four categories, sometimes known as PESO (paid, earned, social, and owned). Paid media usually takes the form of advertising or paid editorials. Social refers to sharing of content by customers and other members of the public, and may involve content produced by the company or paid influencers. Owned media is produced by the company itself. Earned media is not paid-for, but is published voluntarily by third parties. Description 
Earned media is what happens when a person or organization is spoken of by a third party. Examples include mentions in traditional media and ratings and reviews. Sometimes social media mentions and online discussions are included in this category. While marketers can help generate earned media activity, they do not generate it directly. One potential drawback, compared to paid or owned media, is that the person or organization has to convince a journalist to write a story about them, or an editor to publish an outside editorial. While this gatekeeper function serves to filter out lower quality content, it may also allow media outlets to act as censors if they do not agree with the source or its message. Further, because the person or organization does not control the message once it is in the hands of a journalist, media mentions may be negative. As one example, while the 2016 Trump political campaign was cited as having obtained billions of dollars in earned media, one study estimated that 23% of earned media mentions were negative. A Nielsen study in 2013 found that earned media (also described in the report as word-of-mouth) is the most trusted source of information in all countries it surveyed worldwide, and is the channel most likely to stimulate the consumer to action. In a 2019 study by the Institute for Public Relations, participants shown an earned news story, an advertisement, a blog post, and a company blog post found the earned media story the most credible. Readers sought out and paid attention to information such as the independence and credentials of the journalist, the balance of the coverage, and the prestige of the outlet in which the story appeared. References

Public opinion
Public relations
Social influence
Marketing techniques