This chapter is full of details about Winston's work life: from the speakwrite, a contraption into which Winston speaks the articles that will be later written (speaking and writing here considered opposites), to the memory holes in which "records" are thrown, not to be remembered and documented, but to be destroyed. The reader should note that Orwell consistently names items, processes, and events antithetically to their intents, results, and purposes and thereby makes Winston's world more terrible and frightening. The function of the Ministry of Truth, for example, is to create lies; the function of the Ministry of Peace is to wage war.
Here the reader gets the full detail of Winston's work and a better view into the political system of his society. He is engaged in forging the past into something palatable to the Party's ideology: Big Brother is never wrong, heroes are those who put their own lives aside for the Party's benefit, and goods are always manufactured at a quantity beyond what is expected. Of course, none of it is true, and so follows Winston's question, haunting him throughout the book: If a fact only exists in your memory, and yours alone, what proof is there that it really happened at all?