1) The document summarizes two communication theories: the agenda-setting theory and the gatekeeping theory. 2) The agenda-setting theory proposes that mass media has the ability to influence the public agenda by deciding what issues are important. The gatekeeping theory suggests that media filters information that reaches the public by controlling access. 3) Both theories are influenced by social and ideological factors and are subject to criticism that reality may not be accurately portrayed due to the subjective decisions of editors and gatekeepers.