The primary difference betweeen public relations and advertising is that public relations is considered 'earned media' while advertising is know as 'paid media'.

PR or 'earned media' means your product/service/message/story is voluntarily being promoted by a media outlet such as on a television talk show, on the radio, or in a magazine. This type of coverage is also referred to as 'editorial' coverage. Earned media coverage through PR efforts could be in the form of a news anchor or radio DJ on the air talking about your product, being interviewed about a topic as an expert in your industry, or via a variety of other mediums. An agency that offers public relations services can help 'pitch' your product/service/message/story to their network of media partners with the goal of getting you this type of editorial coverage. PR agencies have the experience to know which media outlets would most likely have an audience that would be interested in your content, which means those networks would be the most likely to tell your story, and therefore agencies can effectively target your pitches to the right channels. Media industry professionals often get story ideas from reputable and trusted PR agencies with whom they've built long-term relationships with.

Advertising or 'paid media' means you are paying for a pre-designed advertisement or pre-produced commercial to appear in any number of mediums such as on a billboard, in a magazine, on TV or on the radio. An agency that offers advertising services can help you with this by designing the creative for your print advertisement or producing your radio/tv commercial.

Although with paid advertising you have control over the ad design and/or video production, what info it will contain, where the ad will appear and when it will appear, consumers are still very aware the message on an ad is paid for by the brand/company trying to sell the product/service the ad is about. While there is less creative control with editorial coverage obtained from PR efforts, as the media controls if and when they pick up your story, how they promote your product/service and what is said, there is more perceived value. Hearing about a product or brand/company from a trusted media partner such as a major tv network or magazine gives consumers a completely different perspective than a paid advertisement. If a media person or network people trust is endorsing a product or brand/company by talking or writing about it willingly, it creates an automatic sense of credibility to consumers, drives traffic to the brand, and often results in a spike in sales.