Fahrenheit 451 focuses on Guy Montag, who is a “fireman”. His job, in this dystopia of a world, is to start fires, not to put them out. He and the other firemen get calls that direct them to the houses they are supposed to go burn down.
Why choose those particular houses? The houses the “firemen” are sent to belong to people who have gathered up and hidden away a very dangerous substance that the government does not want the general population to be infected with. The substance in question is books.
All books are banned and destroyed. People found with books are also destroyed, often by the fireman at the scene of the crime.