Well, first it is important to remember that this is not a story, it is an essay, and a very fine example of this literary form. In this essay, Orwell recounts an experience he had while serving as a police officer of the British Empire in colonial Burma. One day, a frenzied elephant went on a rampage in a bazaar, killing one person. By the time Orwell arrives on the scene to deal with the matter, a large crowd of Burmese has gathered to watch. Although he hates his job, which he refers to as "doing the dirty work of the Empire," and does not want to kill the elephant, Orwell feels pressurised by the crowd and his position to take action. If he does not he will risk being laughed at. He therefore shoots the animal repeatedly and clumsily, giving the elephant a painful and slow demise.
Key to this essay is Orwell's comment on colonialism - through this experience Orwell comes to realise that the white man through the power he has taken actually makes himself nothing more than an "absurd puppet pushed to and fro by the will of those yellow faces behind." As he goes on to comment:
I perceived in this moment that when the white man turns tyrant it is his own freedom that he destroys. He becomes a sort of hollow, posing dummy, the conventionalised figure of a sahib.
Therefore, paradoxically, by seizing power over others, the white man actually decreases his own freedom, because he is forced to act in the way that the indigenous population expect.
Hope this helps you grasp the central points of this fascinating essay. Good luck!