Free Verse

Free verse can be meaningfully contrasted against traditional verse and blank verse. Traditional verse generally follows formal rules of both rhyme and meter; and blank verse eschews rules of both rhyme and meter, in favor of a more natural pattern that follows the cadences of the spoken word. Free verse can be understood as inbetween these, in that it maintains traditional schemes of meter while doing away with traditional schemes of rhyme.  

Poetry doesn't have to ryhme

Most people learn eventually that text doesn't have to "rhyme" in order to be a poem. This is because poems can be in free verse. Free verse basically refers to any poetry that does not follow a strictly established meter or rhyme scheme. The opposite of free verse would thus be metered verse. Dr. Seuss often used metered verse, as with his famous Cat in the Hat poem.

The rise and expansion of the use of free verse has generally been recognized as one of the key innovations of modern poetry, as opposed to more traditional forms of composition.

Using free verse in a poem

Here are some examples of how the term free verse can be used within the context of actual sentences. 

"The free verse pattern of the modernist poem left the material so unstructured that it was unclear to some readers whether the text should be identified as poetry proper or as highly lyrical prose instead." 

"In a great deal of free verse poetry, the rhythm, structure, and cadences of the poetry tend to follow the flow of spoken speech: for example, a line break might happen when a person might naturally take a breath."

"Although he was brought up to believe that only metered verse was real poetry, the writer eventually shed this prejudice as a result of feeling a need for greater lyrical freedom in his work."

Just in case you need further clarification regarding the meaning of free verse, here are a couple basic rules you can follow. 

1. Free verse just refers to any poetry that is not in metered verse. So, if a poem lacks either a consistent rhyme scheme and/or metrical pattern, then it is almost surely free verse. Also, free verse can generally be told apart from prose by the fact that it is still broken up into lines. 
2. Free verse has its own internal structures, designed by the individual poet in question. The point is simply that free verse does not draw on pre-established poetical forms, such as couplets or iambic pentameter. 

Free verse shouldn't be confused with blank verse, the absence of formal rhyme and rythym schemes. Read more about blank verses and how it is used in poetry.

Roots found in aesthetic modernism

The rise of free verse poetry is strongly correlated with the cultural movement of aesthetic modernism. Prior to this, poets generally felt obliged to respect the traditional structures of metered verse, including structures of rhyme and rhythm. With modernism, however, poets began to feel that such structures had become ossified and detracted from genuine creativity; so, they began to invent their own free verse structures in an effort to achieve a greater harmony between form and content. Read more about the history of the free verse.

In a way, this was revolutionary at the time, even as free verse has now become more or less commonplace among poets. Of course, poets can still use metered verse, if they want. But a contemporary poet who does this is almost self-consciously hearkening to the classical past. 

Also, the rise of free verse has had the effect of somewhat blurring the line between poetry and prose. For example, Baudelaire's work Paris Spleen could perhaps only be categorized as prose poetry: one gets the impression that it essentially consists of free verse poems that were organized into paragraph form for the sake of aesthetic effect.