According to the Wikipedia, free verse is where a poem does not have to rhyme or have a specific structure / beat. In free verse it is still common to use various poetic techniques such as alliteration, onomatopoeia and repetition.
The Mischievous Cat
There once was a cat with a hat,
Who chased after this and then that.
It knocked over a vase,
Then fled with such grace,
Leaving chaos where once it sat.