Hypnopaedia is teaching children in their sleep. As children in the World State have no parents, they all live in dormitories. Every night they hear repetitions of the ideas that the state wants them to internalize. They listen to these ideas repeated so often that they grow up brainwashed or conditioned into thinking that these ideas are the truth, not merely opinions. The adults also appear to think these are their own ideas and opinions, or at least don't question them or where they come from. Lenina, for example, is constantly thinking that the khaki color the Deltas wear is "beastly," as if this is her own taste, and rejoicing over and over that she is not a Delta. She never stops to wonder why she holds these opinions. They simply seem natural to her.
Hypnopaedia is a form of passive, rote learning and central to the education of children. Nobody, with the exception of Alphas, is taught to think critically or independently, and even Alphas' thoughts are censored.
From what we witness, the hypnopaedia in the World State emphasizes consumerism, conformity, and contentment with one's place in the caste system. While dehumanizing, it allows the social order to run smoothly, which is the highest value in this brave new world—and what Huxley satirizes.