what an essay is, exactly, these days

Zadie Smith wonders what essays offer to a novelist:

Within the confines of an essay or – even better! – an aphorism, you can be the writer you dream of being. No word out of place, no tell-tale weak spots (dialogue, the convincing representation of other people, plot), no absences, no lack. I think it's the limits of the essay, and of the real, that truly attract fiction writers. In the confined space of an essay you have the possibility of being wise, of making your case, of appearing to see deeply into things – although the thing you're generally looking into is the self. "Other people", that mainstay of what Shields calls the "moribund conventional novel", have a habit of receding to a point of non-existence in the "lyrical essay."

These are all satisfactions the practice of writing novels is most unlikely to provide for you. Perfect essays abound in this world – almost every one of Joan Didion's fits the category. Perfect novels, as we all know, are rarer than Halley's comet. And so, for a writer, composing an essay instead of a novel is like turning from staring into a filthy, unfathomable puddle to looking through a clear glass windowpane. How perfectly it fits the frame! How little draught passes through!