Public affairs (PA) is the management process that focuses on the formalization and institutionalization of corporate public policy. Public relations (PR) deal with government as one of many publics and have many communication responsibilities.
Richard Armstrong, former president of the Public Affairs Council, addressed the distinctions between public relations (PR) and public affairs (PA) in terms of their relative emphases, interests, and directions. He submits that the terminology is very important. The principal distinctions he has made are as follows:
(1) Whereas PR deals with government as one of many publics, PA professionals are experts on government, and
(2) Whereas PR has many communication responsibilities, PA deals with issues management and serves as a corporate conscience. 
Part of the confusion between public affairs and public relations arises from the fact that companies use different titles for the same functions, for example, some corporate public relations executives changed their titles, but not their functions, to public affairs.
 Richard A. Armstrong, “Public Affairs vs. Public Relations,” Public Relations Quarterly (Fall 1981), 26. Also see Craig S. Fleisher and Natasha M. Blair, “Tracing the Parallel Evolution of Public Affairs and Public Relations: An Examination of Practice, Scholarship, and Teaching.” Paper presented at The Fifth International Public Relations Research Symposium, Lake Bled, Slovenia, July 1998.