Once a perfect press release or marketing article is written, it needs to be distributed. To optimally reach as wide an audience as possible (as well as many eyes as possible), a business or site will utilize the services of a company or provider for online press release services. There are some providers that charge for online press release service and there are also ways for a company or site to do press release promotion for free or on their own.
Their are benefits and limitations of both but the general thought is an experienced provider would be able to provide a business with wider and more knowledgeable distribution than a company attempting distribution on their own. There are free services available that can provide some help and success with press release distribution and promotion.