There is no one essay with this title that is especially well-known. The saying "All that glitters is not gold" actually originated in "The Merchant of Venice," one of Shakespeare's plays. The commonly accepted meaning of this saying is that not everything is as good as it may appear, or not everything that "glitters" is really worth as much as "gold." An essay about the saying may discuss Shakespeare's play and how the line became a common expression.
In "The Merchant of Venice," "All that glitters is not gold" is the opening line of a poem written on a scroll in the golden casket. The poem tells of many before the character, Morocco, who "sold their souls" to get to the golden casket, but found it wasn't worth it. The casket looked like gold, but wasn't the treasure they had thought.
This relates to the way "All that glitters is not gold" is used as an expression as of 2015. Though not everyone who uses the phrase knows its origin, even on its own, the line makes a good point. People use it to express that some things may be enticing and shiny, but they aren't what they claim to be.
J.R.R. Tolkien twisted this line in "The Fellowship of the Ring." "All that is gold does not glitter" reverses and puts a positive spin on the original Shakespearean line. This line explains that sometimes great things don't look good on the outside, that something beautiful and rare may not "glitter" upon first sight. An essay on this topic may also touch on this modern take on the original quote.