The document summarizes agenda setting theory, which describes how the media can influence the public's perception of what issues are important. It discusses the history and development of the theory, including key researchers like Walter Lippmann and Maxwell McCombs. The theory proposes that the media can set the public agenda by focusing on particular issues and influencing what the public thinks are the major issues. It also discusses how agenda setting can apply to social media and politics. The theory has since been expanded to include factors like how audiences actively engage with media and the influence of different types of media sources.