Propaganda is the use of mass communication channels to further an agenda. Despite being an extremely broad category, the term got a negative connotation after becoming associated with dishonest manipulation of the general public. Popular forms of propaganda, such are advertising and public relations, do not refer to themselves using the term. Most media can be critiqued as functioning as propaganda of some kind, since it inevitably adopts and propagates some political beliefs.
In their book Manufacturing Consent, left-leaning thinkers Noam Chomsky and Edward S. Herman propose a propaganda model for western news media, demonstrating and explaining the way it always ends up defending the interests of the ruling capitalist class.