Public Relations is defined as the professional maintenance of a favorable public image by a company or other organization or a famous person.

Advertising is defined as the activity or profession of producing advertisements for commercial products or services.

The two are both aiming to reach a target audience to either sell or brand their product or company.

The difference in the two is that advertising is paid media and public relations is earned media.

In advertising, you pay to brand your company in the way in which you want to be seen. In public relations, you create relationships reporters or editors so that they write a positive story about you or your client, your candidate, brand or issue based on the information you send them.

In advertising you have complete message control. In PR you have to trust that the relationship you have built with the reporters or editors will give you a positive message.

Another difference is the duration of coverage. In advertising you can pay for an ad to be shown as many times as your budget allows, in PR you can send your press release to a number of journalists who will then publish the story in different ways allowing your target audience to see the information differently in many mediums. This is said to be even more effective than reinforcing the message.

The two differ in credibility. When target audiences view an advertisement they know that it has been paid for by that company trying to sell them something. In PR, stories are written by journalist who have chosen to write on said company or topic. The stories written are usually newsworthy, informative, unbiased articles making them much more credible. PR can connect with target audiences here because they are not trying to blatantly sell them something.