The headline of this section has a hidden meaning, which is, 'essay can be written on any topic'. Suppose something has to be written on God Particle. It is clear that it is a topic of science which will be suitable for either scientists or science students and not for the common man. However, when the topic will be written for everybody, then, it will become an essay. An essay is a mode whose reader belongs to the common section. This is a kind of writing which is written for common people. This common man doesn't need specific information like a scientist or a physics student do. Hence, an essay fulfills our need that every topic is for everyone and at the same time,it is not for everyone.
I am discussing this point as it is very important for essay writing. When you write an essay, your role is that of an effective communicator. In order to communicate effectively you need to know who your target audience is. Only then can you decide. what kind of information should be conveyed and in what style. You have to consider the needs and wants and the grasping power of your target audience. Without it, your essay may prove anything but a fancy piece of writing.