Polyphony refers to music that has two or more independent melodic lines playing at the same time. Homophony, on the other hand, refers to music that has only one melodic line with accompaniment.
In Pachelbel's Canon, the main melody is played by the violins, while the lower strings play an accompanying countermelody. This creates a polyphonic texture, as there are two or more independent melodic lines playing at the same time.