Let's see, I think I'll defer to Mr. Keating here from Dead Poet's Society:
We don't read and write poetry because it's cute. We read and write poetry because we are members of the human race. And the human race is filled with passion.And medicine, law, business, engineering - these are noble pursuits and necessary to sustain life. But poetry, beauty, romance, love - these are what we stay alive for.
For me, poetry has always been about putting intense emotion into a particular form. This is why I absolutely adore writing sonnets. I love trying to take a particular sensory experience and cramming it into a difficult rhyme scheme, ... I get some kind of masochistic pleasure out of it.
I suspect it wasn't too different from many of our favorite poets as well. Look at all of the poetic forms we have: odes, ballads, sonnets, limiricks, ... even songs!!! It's just another form of literature, ... we can lump it into the group with novels and short stories, ... that is, if you want to take the high school student point of view. There is no doubt, however, ... poetry contains the most passion.
This is a very difficult question to answer given that you do not offer a little more in what you would like the answer to focus on. Regardless, I will try to answer your question.
Poetry is a form of art which allows a writer to focus on something which, typically, lies heavy on their mind (for good or for bad). Many times, poets use their pieces as an avenue by which they can express their personal feelings about any topic without feeling the constraint of a minimum word count/page count (as with novels) or worry of fitting into a specific genre (not that any authors typically would worry about this).
When I introduce poetry to my students, we listen to music. Surprise!!! Music and poetry go hand in hand. Musicians are simply poets who have set their poems to sound.
As for what poetry "is all about", there is no simple answer to this question. Poetry is about everything and nothing; poetry is about emotions and lack of emotions; poetry is about hardship and success; poetry is about the apples and the oranges.
Poetry, most of it today, is not set to staunch limitations as to how or what a poet can write about. Even when poets did write within the constraints of a Shakespearean or Italian sonnet, it was the poets choice to write in such a fashion.