Animal Farm is an allegory which uses a fable to pretty much retell the Russian revolution and give comment on it. If you use the link below, you will see how most of the characters in the novel correspond to the major players in the revolution. Farmer Jones represents Czar Nicholas and the way Orwell saw that he treated his people (neglected them in favor of treating himself well). Old Major symbolized Karl Marx, who gave the people a vision of communism where everyone would be equal to everyone else and the people would be in charge of their own destinies. Orwell's feeling about the revolution can be summed up in how he ended the story...where the leaders of the "animalist" group became just as corrupt as the people they overthrew.
This question has already been asked and answered many times here on eNotes. Here is a comprehensive link for you: http://www.enotes.com/animal-farm/q-and-a/tags/russian+revolution