It works as follows.
Person A writes a poem. Person B (that could be you), takes the poem and uses it in a new song/composition - they call it a beat. The result is a poesybeat, which then can be listened to by the masses. The other way round: You make some original music (or upload a demo you've had lying around) - wait til someone else uses your music to write poetry to. The result can be combined into a poesybeat.
The reason I like this so much, is that you collaborate with people from the other side of the globe - it's free, no hassle inspiration and the results are always unique! They compile Albums of poesybeats.
Examples, explanations of the arts initiative can be found at http://poesybeat.org - go check it out for yourself! You can listen to my results there, under my name Marco Aldendorff or VeRCEttY.