Public Relations, referred to as PR for short (not “per,” but P (pause) R), is the interaction between an organization (such as a government agency, a corporation, a school board, a church, etc.) and the public.
Most organizations have a Department of Public Relations or something similar. This branch is tasked with managing relations between the organization and the public.
In practice, however, public relations (PR) usually refers to efforts by organizations to influence the news media.
Media is the plural for medium. In other words, a newspaper, television channel, or Internet website, is an intermediary which mediates between the organization and the public. The “media” (plural!) are between the organization’s message and the public the organization wants to hear (and listen to) that message.
Consequently, PR usually consists of press releases (not to be confused with Public Relations itself), direct communications with reporters, responding to “media inquiries” (questions from reporters), and organizing “press events” at which senior staff speak to the public, through the media (plural!), to present the best “face” that the organization can put forward and preserve or enhance the organization’s reputation.
Public Relations also includes what is known as damage control, that is, limiting the damage done to the organization’s reputation by negative stories in the media (plural!).
When Public Relations becomes an issue of artfully lying without being easily caught doing so, or distorting the truth without “lying” per se, this process is known as spinning the facts, which modern convention has shortened to spin. This can also be called “media spin” or “spinning the media,” the latter creating a mental image of leading reporters around in circles. Actually, it is meant in the sense of rotating merchandise to present the best-looking side, for doing so does not actually alter the merchandise itself in any way – but nonetheless helps to sell the goods.