Winston Smith is the protagonist, or main character, of George Orwell's novel 1984. He works for the government of Oceania, specifically the Ministry of Truth, an organization tasked with changing all records to support the ideology of Big Brother. His job title is records editor in the Records Department at the Ministry.
The Party believes that in order to maintain power it needs to control the flow of information not just about the past but also about the present. For example, Oceania has been at war with Eastasia and allied with Eurasia. The Party, for some reason not known to Smith, decides that they are now allied with Eastasia and at war with Eurasia. In order to maintain control of the truth, the Party insists that they have always been at war with Eurasia and has the Ministry of Truth rewrite history to reflect this. Smith puts in 90 hours at work in five days to make this change, going through past books and newspapers and editing them to reflect the current reality.
Winston's job was to constantly rewrite minor "historical" occurrences so that they reflected the current politics. Keep in mind that the politics changed rapidly and frequently in Winston's world, so his job security was good. If a news report had previously said that, for instance, the wheat crop was going to be good and the price of flour would decrease, but with new political shifts in fighting, several flour mills were destroyed, Winston would rewrite this news item so it read that people were going to have to tighten their belts for the good of the party because the price of flour would go up. Winston's job is an example of sinecure in that it was an easy job requiring little effort, but it was secure, if not lucrative.
Winston works at a very unimportant job in the Ministry of Truth now. He only goes in a couple days a week and even he is not quite sure what it is he does. He works for a,
"sub-committee of a sub-committee which had sprouted from one of the innumerable committees dealing with minor difficulties that arose from the compilation of the Eleventh Edition of the Newspeak Dictionary."
He states that one of the jobs, perhaps the only job, of his sub-committee (which is made up of four other people who are like him) is to report whether commas belong inside or outside brackets.