"Haiku" is a traditional form of Japanese poetry. Haiku poems consist of 3 lines. The first and last lines of a Haiku have 5 syllables and the middle line has 7 syllables. The lines rarely rhyme.
Here's a Haiku to help you remember:
I am first with five
Then seven in the middle --
Five again to end.
Because Haikus are such short poems, they are usually written about things that are recognizable to the reader. A truly traditional Haiku describes an element of nature.
I found the best site for information on Haikus and activities to teach this form to students was: http://www.kidzone.ws/poetry/haiku.htm
Here's one I wrote:
Bright fluttering wings
Dances over the flowers