Children's literature is usually understood as the subsection of literature that is written for an audience primarily composed of children. There are some caveats to this definition, including debates about what kinds of literature actually are appropriate for children. This category is not itself a genre, no more than adult literature can be considered a genre, but actually encompasses many different genres. Literature intended for children has existed since at least the 17th century, when a combination of reduced cost in printing and increased attention to the instruction and entertainment of children made interest in this category of literature more common.
Many different types of books make up the category of children's literature. Picture books, beginning reader books, and fully realized novels are all included in this category. Non-fiction, poetry, and historical books can also be found. Most of these texts share an attention to the development of children as readers and are written to be comprehensible to certain age groups. The thematic elements of children's literature are also often restricted to topics considered appropriate for particular ages.
It is not uncommon for children's literature to have value as entertainment, but most people consider the practice of reading to be important to education. As such, even reading books that are purely intended as entertainment is still considered an educationally valuable activity. Many books go a step further and include explicitly educational content. This can take the form of introducing new vocabulary, highlighting historical details, or rewriting classic stories at levels children can understand.
Some of the first stories in children's literature were retellings of classic tales once told orally to children. These stories often had direct morals that were thought to educate children in proper social values. This feature of children's literature has been represented throughout history, as many children's authors feel that texts that will be available to children must present appropriate ethics. In more recent times, the idea of right and wrong actions in children's books has become more complicated and is often debated when considering children's access to literature in school. Given that adult literature is rarely judged by the ethics of its characters, this can be considered one of the major differences that sets literature for children apart.
While these books must usually be written with children as the intended audience, it is not uncommon for adults to enjoy reading children's literature as well. Likewise, just because a book is appropriate for children does not mean that it will always avoid complex topics. For example, there are many examples of children's books written about topics like the Holocaust and slavery. Children's literature has no limits in terms of its subject matter, but authors who write about sensitive topics must risk offending parents if their work is seen as too advanced for children.