The term deriving from the greek means "multiple voices".
Multiple voices often confuse beginners if notated within the same system, where convention uses different stem directions (which is impossible for whole notes).
In the stricter sense not different voices alson don't qualify for polyphony, but they have also to relate to each other,which is also called counterpoint. In 16th century this was taken to the extreme, e.g. in the mass with 40 voices by Striggio, but typically just a few voices exist as in three- or four-part fugues by J. S. Bach.