Children's literature is, obviously, literature directed toward an audience of children, and is reported to reach the age of twelve.
Nancy Anderson, associate professor in the College of Education at the University of South Florida in Tampa, defines children's literature as all books written for children, 'excluding works such as comic books, joke books, cartoon books, and nonfiction works that are not intended to be read from front to back, such as dictionaries, encyclopedias, and other reference material'.
It also includes stories written by children for children, but the literature that receives the most attention are pieces written forchildren.
I believe that children's literature is defined first by genre: in that it is a specific type of writing that contains everything written for children. A "sub-defining" characteristic, I believe, would be directed to its content (but directly related to their reading level).
Some stories are written purely for entertainment, while others provide factual information. These kinds of books could range from learning about the inhabitants of the Amazon Rainforest to books describing the lives of famous people such as Martin Luther King, Jr., Thomas Edison, or Neil Armstrong (the first man on the moon).
Children's literature covers a wide expanse of readers and related interests, and books in this genre will be read by young readers based also (most importantly, perhaps) on the child's reading level.
For example, a really advanced fourth grade reader might be able to understand and appreciate a story written for a junior high school audience. The more "sophisticated" a reader, the more sophisticated the topic presented, and this may be where more "adult" themes are covered in a different manner than they would be for, let's say, a second grade reader.
Case in point, a second grade child might read a book about why "mommy and daddy don't live together anymore," or why it is wrong to steal. The same topics would be covered in a more advanced way with older kids, often times as the plot in an adolescent novel.
The broadest definition of children's literature applies to books that are actually selected and read by children...they...often enjoy stories which speak on multiple levels. In the opinion of novelist Orson Scott Card, "one can make a good case for the idea that children are often the guardians of the truly great literature of the world, for in their love of story and unconcern for stylistic fads and literary tricks, children unerringly gravitate toward truth and power."
Orson Scott Card presents the argument that children are best at selecting literature that appeals to them that they can interpret on more than one level. This speaks, once again, to the wide range of reading levels children's literature is addressed to.
Rutgers University reports that children's literature also assists the child in not only learning about the world, but in discovering who they are in that world. Yet another segment of the reading population for this age group is identified.
With the information I have read, and what I know of adolescent reading, it would seem that children's literature is defined first by the genre, and second by the reading levels of the children who are reading in terms of their ability to understand what they are reading, and to what depth it speaks to them.