What exactly is an essay?

 

This piece of writing is itself an essay. It has four paragraphs. The first has five sentences, the second has 13, the third has 11, and the last has four. Of the 33 sentences, a few are extremely brief and a few are somewhat long. I would call this a brief or mini-essay. Four paragraphs is usually not enough room for an essayist to need.

On the left is an illustration of Michel de Montaigne. In many respects, he invented the literary form that we now call "the essay".  Centuries before Montaigne, other writers wrote compositions that look to us to be essayistic, but it wasn't until Montaigne that the form took the shape that we know today. 

This video is a little bit dry, but it does give great background information about Montaigne's literary innovation.