Many companies put PR and Marketing in the same department, but there are distinct differences between these 2 functions.
We are all familiar with what marketing does. The purpose of marketing is mainly to assist in sales. As for Public Relations, most companies expect it to help in sales as well, but the main function of PR is to increase long-term awareness and shape the branding image. Marketing is sales oriented with short term activities, while PR is perception oriented with ongoing activities.
There are B2B corporations mistakenly think that they don't need PR since they are not facing the general public, but they forget about PR's other duties such as Investor Relations and Employee Relations.
Another important role of PR is for the public to have someone to contact. We think the more the world is going online, the more flesh and blood interpersonal relations is needed somewhere else, according to the Law of Conservation of Mass.
We make an infographic to explain it better:
(copyright by HSU Communication)