What are the main points of argument in Louis Althusser's "Ideology"? Does "representation" of the imaginary relationship of individuals to their real conditions of existence and ideology interpellate individuals as subjects?

Louis Althusser's ideas about ideology and representation are primarily offered in his 1970 essay “Ideology and Ideological State Apparatuses” (“Idéologie et appareils idéologiques d’état”). It is notable as a critique of Karl Marx’s formulation of ideology. Rather than assuming its falsity, Althusser puts forward the idea that ideology the medium for obtaining meaning in everyday life. Particularly important is Althusser’s discussion of the institutions that create and sustain ideology, namely school, church, and state. These relate closely to Marx’s concepts of the ways that social reproduction proceeds. For instance, school—that is, the educational system—exists primarily to introduce and enforce commonly held ideas about society, in service of its perpetuation, and not to encourage people to think independently.
Individuals, therefore, cannot exist apart from society but are conditioned from birth to exist within in, and subjectivity is conceptually impossible outside of socialization. Human perception, even of the natural world, is mediated through representations that are themselves based in the ideologies of the particular society in which they were developed.