"Animal Farm" is a fable of great symbolism. The novel can be seen as the historical analysis of the causes of the failure of communism, or as a mere fairy-tale; in any case it tells a good story that aims to prove that human nature and diversity prevent people from being equal and happy.
The farm animals rebel, drive out Mr. Jones, the farmer, and attempt to rule the farm themselves, on an equal basis. What the animals seem to have aimed at was a type of communism, where each would work according to his capacity, respecting the needs of others. The venture failed, and "Animal Farm" ended up being a dictatorship of pigs, who were the brightest, and most idle of the animals.
So, the animals create their Seven Commandments trying to create equality. The pigs, however, being the natural leaders, managed to reverse the commandments, and through terror and propaganda establish the rule of an elite of pigs. Was this a fairy-tale or the truth?