A repressive state apparatus is what controls you through force or the threat of violence. This includes use of police, courts, and prisons. I believe Althusser called it repressive, to depict the act of using power, force, or violence to control and restrict limitations on individuals freedoms. An example of this would be the prison system. The prison system is used to penalize and detain those who have broken a law, serving as a structure to maintain control and repress those who challenge the states authority.
Ideological state apparatuses are used to prevent change to the state of affairs. These organizations use ideology to sustain control by shaping people’s belief’s, values, and principles without the use of direct force. For example, the education system plays a key factor in how people envision society, authority, and social norms. This also includes maintaining social order by shaping individuals identities and positions in the world with the use of regulations, schedule adherence, and obedience.
RSA’s and ISA’s differ from each other by their control mechanisms. Aforementioned, RSA uses force or the threat of violence in order to subdue those who defy the states authority or break the law. An example of using physical means would be, the prison system physically detains and confines those who have been convicted of a crime. ISA on the other hand, uses ideology to structure values and beliefs. For example, schools promote the social norms and beliefs of authoritative figures, while the media perpetuates narratives around political and cultural ideologies.
The image below represents Ideological state apparatuses. It shows how corporate influence and conformity influence society. ISA’s prohibit people from challenging or working to alter the structures that sustain control within the hands of a powerful bunch.