If you’d like to differentiate between a Polygon and a Face, I’d say a Polygon is 1-dimensional (like a circle) and a Face is 2-dimensional.
Or, a Face is what you can Select in Face Select Mode and a Polygon is the Edges of that Face.
But I almost always use the terms as being interchangeable. Nobody will call the CG police on you.
And now we can also say that a Face is a dude (or a piece of paper) 😉
