Marketing and public relations are two distinct, though closely related, disciplines.
Marketing can be thought of as taking a product and creating a market for it through the use of pricing, promotion and placement.
Pricing – determining an appropriate price for the product, taking into account costs of manufacturing, overhead, competitive pressures, etc.
Promotion – creating attention to and interest in the product via the use of advertising, discounting, samples, and so on.
Placement – establishing an appropriate channel for consumers to find and purchase the product. Determining that selling motor oil might require a channel to garages, to service stations and the regular vehicle owner.
In some cases, a marketing firm might use its experience to recommend that there’s a profitable customer base out there for decaffinated, diet, lime-enhanced orange juice with extra calcium, and work with the supplier to tailor the product to the customers.
Public relations, in its broadest sense, is simply a channel of communications between an organization and the public. What we in the U.S. normally think of as public relations is primarily getting the organization’s message out through a third party (the media, word-of-mouth, etc.) In other words, creating “buzz.”
If I’m a movie star, I want to build and keep a fan base that will see my movies, thus showing the producers that I’d be a good choice to cast in their next blockbuster. My public relations firm sets up interviews with media, coordinates my personal appearances, tries to ensure that the photos of me visiting a children’s hospital get in the paper (and the ones of me leaving a crack house at dawn, don’t) and in general shows me off in my best light.
If I’m a widget, my public relations firm tries to convince the widget-buying public that I’m the best widget in the world, by distributing engineering studies that show my widget superiority, making sure that celebrity widget users only use me, sponsoring widget rallies, handing out samples of me to people in hardware stores and so on.
Does that help?