When you can boil a whole experience into a few words that, carefully chosen, can be read by many people and evoke in them an experience that is not exactly the same but the same on some level.
Our lives are filled with conversations - with others and with ourselves. These conversations are a form of poetry or prose because they encapsulate thoughts or events into translations (ever listen to Jack Johnson's music?) When I read poetry, I translate that set of words into thoughts that I then mirror into some aspect of my life.
I write poetry sometimes and have documented some parts of my experiences in life this way. I can't go back to the time when I wrote those poems and every time I read one it causes me to translate the experience again through the new eyes of my life since the time I wrote it.
Poetry is really encapsulated life. It is more than its content.