Public Relations can be boiled down into two main responsibilities: promoting a brand and protecting it. On the promotional side of PR, professionals help businesses or individuals develop a positive reputation with the public through various unpaid or earned forms of communication, like placements in traditional media, social media, and blogs. On the protective side of PR, they help their company or clients maintain their public reputation or defend it during crises.
To learn more about the promotional and protective sides of PR, including sample PR position titles and salaries, check out this blog post. You can also follow the Public Relations Society of America (PRSA) blog for current news and trending topics in PR.