In the classic dystopian novel 1984, George Orwell writes of a society in which not only speech, but also thought, is controlled. Orwell wrote the novel at the close of World War II, and he modeled Big Brother after notorious tyrannical dictators such as Joseph Stalin and Adolf Hitler.
In the society that Orwell postulates, ideology is forced upon its citizens by the Ministry of Truth, and any past history that does not conform with governmental decrees is expunged or altered. Undesirable people and opinions are simply erased from history. Surveillance is carried out on all citizens by the Thought Police through the technology of view-screens, hidden microphones, and undercover agents planted among the common people. Any deviation from approved speech is severely punished.
Freedom of speech is a concept that goes back at least as far as the ancient Greeks. The Merriam-Webster dictionary defines freedom of speech as "the legal right to express one's opinions freely." In the United States, it is guaranteed by the First Amendment, which states:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for the redress of grievances.
We can see then that the society that George Orwell writes about in 1984 is the opposite of a society that allows and encourages free speech. Orwell uses this contrast to show how horrible a world without freedom of speech would be, so that people would be encouraged to appreciate and hold on to their freedom.