What is the nature of literature?
The nature of literature is quite an open one. It does many things and accomplishes many purposes. One such end is that it helps to articulate conditions within human beings that can find relation in the lives of others. It seeks to relay such narratives so that bonds can be formed with characters, predicaments, and ideas in the hopes of sensing more about our own senses of self. Literature's nature can take on many forms in the accomplishment of these purposes. Yet, the idea present is that within all literature there is some level of articulation of a predicament that can be appreciated by many and help more to understand more of themselves, their worlds and settings. Sometimes, the nature of literature can have a moral purpose, yet other times it might not. However, its primary nature is to "simply connect" with others in its attempt to detail more of ourselves and our world.
The nature of literature is very open-ended and could be answered in many different ways. I would say that the difference between literature and writing that is not literature would be the function. Literature functions to entertain and/or education. What I mean is, as opposed to advertising or explaining, good literature stands on its own as a good or great story. It has developed characters and a setting and an identifiable plot. It has a conflict and resolution that is played out in the story line. It tells a story and has a narrator whether it is first person narrator or omniscent narrator. When we read literature we can love it or hate it or whatever because it's not true. We are not expected to believe it as the truth. In the end, however, we can learn a lot about how people interact and how they speak as opposed to how they think. We can learn to examine our own thoughts and actions through comparing them to the literature we read.
In addition to all that, we can learn how to write by reading literature. It can be instructional.