what is the difference between an "essay" and an "article"?

Answer 1

Very little in practice, except that an essay usually develops some form of argument and therefore begins with an introduction, has a number of intermediary paragraphs in which the argument is developed and then arrives at a conclusion which is set out in the final paragraph.

An article does not necessary develop an argument or even display a point of view. It is simply a succinct way of imparting information. Because it is aimed at a readership which seeks to be informed rather than entertained, it has shorter paragraphs than an essay. In other words, it is more punchy. It is likely to contain links and references and while being neatly rounded off at the end, does not necessary present any conclusion.

That's the theory, anyway!