PR predominantly involves ‘free media.’ The purpose is to develop a discussion and generate coverage without directly paying for it, which is distinct from advertising. Public relations is about selling a company or brand through positively managing the communication channels between a company and its stakeholders and developing a positive reputation.
The 'relations' part of public relations is most important. A good PR team will build connections and partnerships as well as options for collaborative working with prominent figures, social influencers, media taste-makers and journalists.
A great public relations team, however, will build lasting relationships by working as a bridge between your needs and the needs of the media.