What are the agenda setting and gate-keeping functions of media?

Typically agenda setting in the media refers to more news shows, talk shows, and other opinioned forums.  Some entertainment programs could be brought into this field, but generally they are not.

 The agenda setting is the topics of discussion that is communicated.  The information being communicated is to keep us informed.  Some may argue that the context in which the information is relayed may mold our personal opinions.  Everything from the order information is communicated, time allotted for the given subject, and the importance expressed with the content is part of the agenda setting.

The gatekeepers in the media are the individuals that control the information that is communicated.  Essentially the gatekeepers write the agenda.  The topics selected for transmission of communication is difficult.  What is important to one person may not necessarily be important to another.  Also the personal bias of the gatekeepers could result in opinioned information being communicated.  So instead of avoiding splitting an audience or interjecting personal opinion, the gatekeepers try and communicate information that will attract the audience.  So it's not always the most important information being conveyed.