Oppression can be classified into (3)three distinct categories, which include:
(1)external,
(2)internal, and
(3)horizontal oppressions.
External oppression occurs when an individual, group, or force with privilege and/or power harms an individual or group without those privileges. The most viewed example of this would occur when a man rapes a woman.
Internalized oppression occurs when an oppressed person believes and acts upon the negative message being brought upon them.
Horizontal oppression would be the opposite of internalized oppression in the sense that the oppressed lash out against the oppressor usually due to anger and sense of powerlessness.
Internalized and horizontal oppressions are both really a subcategory of external oppression and branch off it. This is because the external oppressor leads the oppressed to react in an internalized or horizontal form of oppression towards another individual or group.