Animal Farm by George Orwell is one of the many well-known books and fables that use animals to tell a human story. Jungle Book by Rudyard Kipling, Winnie-The-Pooh by A A Milne and The Tales of Beatrix Potter to name just a few, also use elements of the same technique.
This literary device is called anthropomorphism and it is a form of personification originating from the Greek words for "human" and "shape."
Animal Farm is also an allegory, metaphorically representing events concerning the Russian revolution. It is politically motivated, criticizing the capitalist West and the totalitarian regime emanating from Russia and similar communist countries.