Haiku is a type of poetry that originates from Japan.
Traditionally the haiku was written in one long string, from top to bottom, using 17 onji (sound-symbols). These onji are usually divided into 3 sections, the middle one being slightly longer than the others with a pause at the end of the first or second section. This type of poetry attempts to convey a feeling or experience through the use of images drawn from nature. Instead of stating a feeling it says "This is what I saw; perhaps it will rouse in you a feeling similar to mine when I experienced it." Here's an example:
I pay the vendor
open the cage of birds,
they fly away in melody.