Homophony is where the different parts of the score move in harmony. A good example would be "Chopin's Nocturne in E, Op. 62 No. 2."*
Polyphony, however, exists when the parts of the the score move completely independent of each other. "Johann Sebastian Bach's 'Fugue No.17 in A flat', from 'Das Wohltemperirte Clavier' (Part I)"**, is an example of polyphony.
*http://en.wikipedia.org/wiki/Homophony
**http://en.wikipedia.org/wiki/Polyphony
Rathorius