Description of Essay

What distinguishes the essay and not an essay? To answer this question can be done with reference to the opinions or formulations that have been there, but the opinions or formulas that already exist are often incomplete and sometimes contradictory, so it still contains shortcomings as well. For example regarding the size of essay, there is a claim-free, medium, and can be read at one sitting; about the content of the essay, there are states in the form of analysis, interpretation and description (literature, culture, philosophy, science), and thus also about the style and method of the essay, there is an opinion states that essay is free and there is also states regular.