Each line of the sonnet is composed in iambic pentameter. Free verse is a poem that has no form. There is not a specific number of syllables or any rhyme. These poems almost appear at a first glance like short pieces of prose. What sets them off from prose is the use of intense imagery and description.
Free verse is also on one very specific theme, which is one definite way to know that it is poetry.
Some authors use punctuation when writing poetry and others do not. This is a very personal choice. Some poets do not use capitalization either. Again, this is part of the creative writing process. After you come up with an idea for a story or poem, remember to close your eyes and visualize it.