The research on the agenda-setting of media is intended to explain how the salience of issues in the news affect the public's perception of their relative importance. There are three commonly identified types of agendas: public agenda, media agenda and policy agenda.
Public agenda setting occurs when the public is the one who decides what is reported (for example, when the issues that matter to the public during elections are reported by the media). Media agenda setting, instead, is when the media considers the agenda for which stories are considered relevant (for example, when the media reports on little-known issues they believe are important). Finally, policy setting is when both the public and the media agendas influence policy making (for example, when the media and the public force a debate in the government).