A square (or rectangle) uses two triangular polygons.
When it is drawn by the GPU, yes, but until that point you can consider a square or rectangle to be a polygon. If you don't, then there's no sense differentiating between "triangle" and "polygon."
When it is drawn by the GPU, yes, but until that point you can consider a square or rectangle to be a polygon. If you don't, then there's no sense differentiating between "triangle" and "polygon."