Animal Farm is a didacticA text that tries to teach a lesson. text - Orwell aims to teach the reader a number of lessons on:
class
equality and inequality
power, control and corruption
These themes are explored through the events and characters in the novel, and are an allegoryA story or poem which has a hidden (usually political) meaning. for the Russian Revolution.
The animals' unhappiness represents class struggle, this leads to the Rebellion which offers some equality.
Then the pigs' actions allow inequality back on the farm.
The theme of power and control is explored throughout the novel and is highlighted by the characters' relationships on the farm.
The themes are political and explore what happened within Russian society in 1917 onwards. Orwell originally subtitled the novel 'a fairy story' suggesting he intended it as a fableA type of story with animals as characters. It teaches the reader a lesson.
It is important to remember that even though the novel is based on events that took place in 1917, the themes are still relevant today.