Importance of keeping the public informed: (1) it creates public awareness of situations/conditions/events, etc.); (2) it facilitates public understanding of issues or concerns; (3) it influences the public in forming opinions/views; and 4) it guides the public in making a decision on the course of action to take.
Information dessimination can be made through verbal communications (e.g. discussions, meetings, lectures, interviews, symposium, ratio/tv plugs) and non-verbal communications (e.g. letters, memos, publications, manuals, banners, stickers, pamphlets, posters, newspaper prints, etc.)
Influencing and motivating the public to a desired line of thinking and action goes well beyond info dissemination. The role of effective advocacy comes in. The bottomline of advocacy is to make the informed and influenced public take concrete action according to the purpose or objective of the communicator or advocate. Generally people are motivated to act when they see benefits to them. If communications is ineffective - there will be no public support or cooperation.