The main point of Animal Farm, by George Orwell, is to criticize communism, or at least the way that communism was implemented in the Soviet Union.
The book shows how the communist movement starts with talk about helping the people and about letting everyone have a voice in their own lives. But then it quickly evolves to the point where the communist leaders (Napoleon the pig, etc.) are no better than the people they replaced. They put themselves above the common people and they run things tyrannically, driving out those they disagree with (Snowball because of the windmill).