Controlling which topics receive attention — not necessarily what's said about them. By making certain issues prominent and others invisible, the media (or any content producer) shapes what the audience considers important.
During an election cycle, if every news broadcast leads with immigration coverage, voters will rate immigration as the most important issue — regardless of whether it objectively affects their lives more than healthcare, economic policy, or foreign affairs. The coverage didn't tell them what to think about immigration; it told them to think about immigration.
Salience is a powerful cognitive bias. Issues we encounter frequently feel important by virtue of that frequency. We don't have an internal monitor that says "this topic is being overrepresented relative to its real-world impact." We take the prevalence of coverage as a rough signal of the topic's importance.
Noticing which issues consistently receive extensive coverage and which receive minimal attention — and asking whether that ratio reflects actual impact or serves particular interests.