Fairy tales are a form of folk literature which are usually intended for children, unlike other types of folk literature, such as tall tales, for example. Despite this, fairy tales can be dark in nature, and don't always feature happy endings. Fairy tales are characterized by the use of a magical or strange world in which the action takes place, and these stories often feature otherworldly creatures such as talking animals and monsters, as well as magic. An example text would be the Grimm Brother's "Children's and Household Tales," published in 1812, which contains many fairy tales still popular in the 21st century, like "Hansel and Gretel."
Often intended for especially young children, picture books are an entire genre to themselves, even though children's literature of any genre can contain the occasional illustration. The key difference is that a picture book relies almost entirely on its illustrations to tell the story, with the author adding only a small amount of text per page. An example would be "The Very Hungry Caterpillar" by Eric Carle.
The school story is a genre of children's literature which is concerned with the exploits of kids attending an educational institution, typically a boarding school. The protagonists in these tales are the children themselves, and plots revolve around the kids' interactions with teachers and school bullies, for example, as well as the general experience of growing up. Many famous school stories originate in England, such as "Tom Brown's School Days" by Thomas Hughes, but have since gained popularity in other countries.
Fantasy tales depict imaginary worlds and unlikely scenarios. At the heart of much fantasy fiction is the struggle between good and evil, with the heroes of such literature facing overwhelming odds and relying on virtues such as courage and friendship to win the day. Fantasy fiction differs immensely in its setting, but fantasy authors often draw on elements of myth, fairy tales and the supernatural to create their plots, characters and settings. An example would be the "Harry Potter" series by J. K. Rowling.
Some poetry is aimed at kids, and while the subject of such works varies, children's poetry often features amusing language and themes, as well as an emphasis on rhyme schemes which make the poetry fun to read aloud and to listen to.
Not all children's literature comes in the form of stories. Plenty of nonfiction literature has been written for kids; much of this is educational in nature, teaching children about subjects such as history or basic science in an accessible manner. Children's encyclopedias are also available.