Imperialism is a policy or ideology where a country extends its power and influence over other nations or territories, often through military conquest, colonization, or economic domination. It typically involves the subjugation of one group by another, leading to cultural, political, and economic changes in the dominated region. Historical examples include European colonization of Africa and Asia, where imperial powers exploited resources and imposed their cultures on local populations. The consequences of imperialism often include social upheaval, resistance movements, and lasting impacts on global relations.