Old Major, a pig on Manor Farm, states that the animals poor living conditions are caused by Mr. Jones, the farmer owner. He proposes that the animals rebel against Mr. Jones in attempt to better the lives of all of the animals.
A few months after Old Major dies, the animals decide to rebel. They are able to kick Mr. Jones off of his farm. They place the pigs in charge because they are the most intelligent animals on the farm.
The Seven Commandments, the law of the farm, are established. Mollie and Snowball flee the farm due to the pigs dominant role that only benefited them. The animals who associated with Snowball after he left were executed.
The pigs don't complete any manual labor, yet they have the best living conditions on the farm. The pigs decide to use the windmill, which was previously promised to better the lives of the animals who completed it, to make generate income.
Animal Farm is prospering even though the animals aren't. They are starving and overworked, but they continue to work because their inspiration, Boxer, is highly motivated to continue working. After his death, the animals start to lose trust in the pigs, for they think that Boxer was sent to a slaughthouse.
The pigs have changed the Seven Commandments so much that they are able to get away with anything. They start to adopt human characteristics while the other animals continue to work in terrible conditions By the end of the book, George Orwell makes it clear that it is hard to distinguish a human from a pig due to their similarity.