What the $%&@! is "Expository Composition"?

Not really sure if I am doing this right but I will give it a shot. When I look up the definition of the term it is this: writing that conveys information and explains ideas. What exactly does this mean? It seems to me that expository composition is any form of writing that is somewhat based on an opinion. If your writing explains an idea, whether it is your idea or not, it would be hard to write in a complete non-biased way. Expository composition also conveys information to the reader. This information that is being conveyed may come from one side of the spectrum or the other, again, in a biased way. This is my opinion on what expository composition is, and you may have another, but isn't that the whole point of it? You are reading this and hearing my side of the story and I think it is great that I get to hear yours. I love looking from the outside in upon arguments and hearing both sides of the story. What do you believe the meaning of "Expository Composition" is?