What is an exposition?

The school project ask me to make a blog and write something about the topic.

So, here are the results that I get from surfing websites^^ :

According to wikipedia, Exposition means, a different type of dramatic structure in which undepicted plots elements are conveyed in dialogue, description, flashback or narrative.

According to wiki.answers.com, Exposition means, a speech or paragraph that conveys information. It's a way to get information out to the read about character and story.

According to Dictionary.com, Exposition means
–noun
1.
a large-scale public exhibition or show, as of art or manufactured products: an exposition of 19th-century paintings; an automobile exposition.
2.
the act of expounding, setting forth, or explaining: the exposition of a point of view.
3.
writing or speech primarily intended to convey information or to explain; a detailed statement or explanation; explanatory treatise: The students prepared expositions on familiar essay topics.
4.
the act of presenting to view; display: The singer gave a splendid exposition of vocal talent.
5.
exposure (def. 10).
6.
the state of being exposed; exposure.
7.
Music. the first section of a fugue or a sonata form, in which the principal themes normally are introduced.
8.
(in a play, novel, etc.) dialogue, description, etc., that gives the audience or reader the background of the characters and the present situation.

In fact, I don't really know what actually it is about. So all I can do now is surfing in the internet
and find more info about it.

One more thing, I think I'll be learning about it soon..