What causes the rounded appearance?

Very basic question, (basic enough to go on this forum I hope)…

I imported an Obj-file into Blender to modify it a bit and use it for a project. The model itself looks very smooth/scultped/buttery compared to my other models that were more “blocky” (not necessarily in a bad sense, just different). I suspected that the rounded look of the model would come from a lot of vertexes and repeated smoothing, but as you can see on the picture, there aren’t that many vertexes either. Each vertex just appears shaded instead of monochromatic.
I guess what I want is that each face should always have the same color through and through, in order to make it more sharp.

you can see here.

Flat versus Smooth shading

…Can’t believe I missed that. Sorry!
But thanks anyway!